The Grateful Dead, The Electric Factory and The Spectrum, 1968-77 (Philadelphia Story)

The Grateful Dead played The Spectrum in Philadelphia 53 times

Philadelphia was America's first great city, but by the end of the 18th century, it had started to be eclipsed by New York, which was just 90 miles to the North. Yet Philadelphia has continued to be one of America's great cities ever since then, by any accounting. However, it has suffered from proximity to Manhattan, in that Philadelphia is always compared to New York in a way that other cities are not, and it minimizes the importance of Philadelphia itself. Philadelphia and the history of The Grateful Dead are no different; Philadelphia played an absolutely central role in the national importance of the Dead, and yet you would never know it. New York swallows up the East Coast history of the Dead, and the crucial role of Philadelphia gets lost. This post will look at the history of The Grateful Dead's concert appearances in and around Philadelphia, with a special emphasis on The Spectrum, the most critical venue for both the band and the city.

The Philadelphia Spectrum was at 3601 South Broad Street, at the South end of Broad Street, built in 1967 for the expansion Philadelphia Flyers and also to accommodate the 76ers, with an initial capacity of around 15,000. The Spectrum looms large in Philadelphia history. In a sports-mad town--you have no idea--the home of the Flyers and the 76ers from 1976 to 1996 was going to loom large in the memories of Philadelphia residents and fans.

As if sports weren't enough, The Spectrum was the crucial concert venue for Philadelphia well into the 21st century. All sorts of legendary rock events took place at the Spectrum, like Cream in 1968, Hendrix in 1969 and 42 Bruce Springsteen concerts, just to name a few. The Grateful Dead topped even Bruce, playing the Spectrum 53 times. Yet Grateful Dead history focuses on New York and San Francisco, for better or worse, so the critical role of other cities and promoters gets lost. This post will look at the crucial history of the Grateful Dead in the Philadelphia area, and in particular the arc of how the Grateful Dead worked with the Electric Factory promoters to become a staple of the Philadelphia rock scene.

This Is All A Dream We Dreamed by Blair Jackson and David Gans (Flatiron Books 2015) is the definitive oral history of The Grateful Dead

Touring To Build An Audience in the 1970s
It is now common to try and retell Grateful Dead history as if they were radical business innovators, foretelling the internet age before there was even an Internet. Perhaps they were. When the Dead staked their claim in San Francisco, and then made landfall in Manhattan in 1967, they were doing things their own way, in defiance of reality and good sense. Yet the Dead managed to survive professionally, and thus their legend was born. After San Francisco and Manhattan, the Dead next conquered New Jersey and Philadelphia, which are side by side. There were some accidental elements to New Jersey's ascension as the East Coast Deadhead stronghold, but the Dead's conquest of Philadelphia was not only more conventional, it turns out that it was planned.

The world's two leading Grateful Dead scholars have a new and important book that will be a boon to bloggers like me for the rest of our days. This Is All A Dream We Dreamed: An Oral History Of The Grateful Dead, by Blair Jackson and David Gans, has been released by Flatiron Books just in time for Christmas 2015 (if you get it now, you can finish reading it before you wrap it as a gift). Instead of a retread of the already-known, Jackson and Gans have a vast trove of new interviews with those who were there. By now, enough time has passed that truths can be told, and history can be seen more clearly. A quote from early-70s tour manager Sam Cutler explains the Dead's touring strategy.

Sam Cutler: The art of touring is to tour with a specific end result in mind.  I'll give you a quick, classic example.  Rock Scully was very central to all of this.  Rock was really the only guy in the Grateful Dead who understood the centrality of FM Radio to what the Grateful Dead were doing. There's a way in which FM Radio could be used to reach markets that, hitherto, hadn't been touched.  So, for example, in Pennsylvania, you wanted to do a gig, let's say, at the Spectrum in Philadelphia, that holds 18,000 people, you obviously can't just walk into the Spectrum, and be, you know, David Gans or the Grateful Dead at that time and promoter goes "we'd love to put you on at the Spectrum, but you aren't even going to sell 800 tickets.  It's an 18000-seat venue" So the question becomes, how do we get this band into, make this band in such a way, that they are exposed to enough people that they can sell out the Spectrum.  Well, one of the clues to that, keys to that, was FM Radio.  And one of the specific keys to FM Radio was actually college radio stations, because the amazing thing is that everywhere in America, to this day, there's college radio stations in New York, Philadelphia, wherever you want to be.  So what we did was we took Pennsylvania, as a market area, and worked on playing at different colleges where there were 15-20000 resident people.  We used the FM Radio station in that market to reach more people [p.184]
[Sam Cutler interview with David Gans: July 29, 2014, Saugerties NY]

When we unpack Cutler's remarkable quote, it transforms numerous truisms about the Grateful Dead.
Truism: When Lenny Hart bankrupted the Grateful Dead in 1970, they had no choice but to tour relentlessly for any paying gig

• Reality: the Dead had to tour for income, yes, but Sam Cutler had a plan

Truism: Rock Scully was an old pal, Jerry's drug buddy and teller of tall tales

• Reality: Rock was Rock, of course, but per Cutler he understood the newly-formed rock market as well or better than anyone else at the time--if you don't believe me, who's bigger today from back then, the Grateful Dead or anyone else (hint: Fare Thee Well)?

Truism: The Grateful Dead were just mellow, sincere hippies who caught the rising tide

• Reality: The Dead worked hard for success, their plan worked and they succeeded. The fact that no one saw it as a well-executed plan by a hard-working band isn't their problem

Truism: The Grateful Dead's FM broadcasts of concerts in 1971 broke them to a whole new market\

• Reality: The 1971 FM broadcasts were essential to the Dead's national concert success, but the Dead had locked into the importance of FM radio the year before, and used it to their advantage before other bands really caught on

A newspaper ad for The Electric Factory in Philadelphia in March of 1968, soon after the venue opened. The Electric Factory mostly advertised on radio, so there were very few display ads and almost no posters for the venue

The Electric Factory, The Spectrum and Philadelphia Rock Concert Promotion
Compared to the rock concert history of some cities, the Philadelphia story is pretty straightforward. After a few fledgling folk clubs tried to book electric music back in 1967, two young guys and some 30-something bar owners opened The Electric Factory. The Electric Factory, at 22nd and Arch Streets (2201 Arch), near downtown, had recently been a tire warehouse. The 2000-capacity room immediately became Philadelphia's psychedelic rock headquarters, and every hip 60s band played the Electric Factory, including the Dead.

The Electric Factory was open from February 2, 1968 until the end of 1970, when the room simply became too small for the ever-expanding rock market. However, the Electric Factory team had been promoting shows at the much larger Philadelphia Spectrum, just south of downtown, soon after it's opening in 1967. Thus the Electric Factory were the principal Philadelphia rock promoters from 1968 onwards, not only at the original venue but at the Spectrum and around the entire region. The Electric Factory can be favorably compared to Bill Graham Presents in San Francisco, where a single organization was booking the same acts from the 60s through the 90s. Electric Factory Concerts remains the dominant promoter in Philadelphia, though it was subsumed by SFX (now Live Nation) in 2000, just as Bill Graham Presents had been a few years earlier.

However, back in 1970, just as now, if a rock band wanted to play the biggest venue in Philadelphia, they had to go through the Electric Factory. The biggest rock venue in Philadelphia was the Spectrum, and the Grateful Dead did not play it until 1972. However, as Sam Cutler's quote shows, they had been working towards the Spectrum from 1970 onwards. Fortunately for the Dead, their roots went as deep as any other 60s band with the Electric Factory promoters. 

Electric Factory Concerts
The five partners who began The Electric Factory in Philadelphia were from different universes. Larry Magid had gone to Temple University and onwards to New York, where he had become a talent agent for the huge General Artists Corporation, one of the largest Talent Agents in the country. He worked with some of the younger acts on their roster in the mid-60s, However, as "the new guy," he got to book the likes of Jimi Hendrix and Big Brother, since no one above him who knew who they were.

Magid booked some jazz acts in Philadelphia as well, and one of the places he booked them at was a club called The Showboat, on Broad and Lombard. Herb Spivak ran The Showboat, and along with his brothers Allen and Jerry, he booked jazz concerts around the Philadelphia area. The Spivaks were in their 30s at the time, so they had eventually taken on a younger partner, Shelley Kaplan. Magid had known Kaplan at Temple, so when opportunity beckoned, the three Spivak brothers and the younger Kaplan and Magid made a good team.

Philadelphia was a huge music town, but while Fillmore-type venues were opening all over the country in 1967, no one had succeeded with one yet in Philadelphia. There had been a few places like The Kaleidoscope and The Trauma, but they were small and unable to absorb the wave that was about to come. The five partners recognized that there was going to be a growing rock circuit, and wanted to be in on it. Herb Spivak had found a building at 22nd Street and Arch, a former bakery, a former Pointiac dealership, and then a tire warehouse. He obtained the lease, and The Electric Factory debuted on Friday, February 2, 1968 with The Chambers Brothers. The soul of Philadelphia was immediately psychedelicized, and the Electric Factory was an instant hit.  The Electric Factory put on shows downtown most weekends through the end of 1970, except when it got too hot in the summer for the not-air-conditioned venue.

April 26-28, 1968 Electric Factory, Philadelphia, PA; The Grateful Dead/Amboy Dukes/Edison Electric Band/Beymont
The Grateful Dead's first performance in Philadelphia was a weekend (Friday>Sunday) booking at the Electric Factory. The band had just come from a two-weekend stint in Miami that had started poorly, but had ended well. By early 1968, The Dead's first album was over a year old, which made them Last Year's News in rock terms. They shared the bill with a rising band from Michigan, The Amboy Dukes, whose album and single "Journey To The Center Of Your Mind," had just been released in April (you may be familiar with Amboy Dukes lead guitarist Ted Nugent).  There were also two local bands. The Edison Electric Band featured bassist Daniel Freedberg, later better known as "Freebo" (he worked with Bonnie Raitt) and organist Mark Jordan, later a successful LA session man (with Dave Mason, Jackson Browne and many others).

In his 1996 book Living With The Dead, former Dead road manager Rock Scully made great sport of the fact that on this Philadelphia trip, the band were put up in what appeared to be a house of ill-repute. It appeared that there were mostly African-American prostitutes and their clients using the hotel, and they mostly hung out in the blues bar on the ground floor. Scully doesn't name the promoter of the hotel, but it doesn't take much research to figure it out. Garcia and the others were very disturbed, according to Rock, and insisted that he find generous co-eds to put them up for the weekend. In Scully's book, the Dead are glad to make tracks from the hotel, except of course for Pigpen, who hung out in the bar all weekend and was apparently ready to move in.

In 2011, Larry Magid produced a career retrospective, My Soul's Been Psychedelicized: The Electric Factory-Larry Magid with Robert Huber (Temple U. Press, 2011). Magid's memoir covers over 40 years in the music industry, and it actually has relatively little prose, as the book is mainly vintage photos and posters. Nonetheless, Magid takes the time to comment on Scully's slight, pretty much the only criticism he levels at one of the acts that played for him.

The Dead performed several shows at the Factory in '68. They weren't great musicians, apart from Jerry Garcia, and they didn't yet have a popular song that readily identified them. Their initial appeal was in the way that they lived--as a commune. The sweet sense of a new rolling movement defined them. One weekend the club loaned them the Electric Factory car, a '59 Cadillac Limo with big fins and a psychedelic paint job. The Dead loved tooling around the city in the limo, although they were less enthralled by the accommodations offered at the Douglass Hotel above the Showboat at Broad and Lombard, the Spivaks three-dollar-a-room joint, where a lot of the guests stayed maybe an hour. Garcia and his bandmates found the Douglass way too funky. For years, they would tease Allen Spivak and me about it: "You put us up at that place." (p13)

So Magid concedes Rock's story, disses most of the band, makes the point that they liked the car, and acts as if the hotel was just fine, a scant 43 years after the event. Grudge much?

update: a Correspondent sent a great link about the Douglass Hotel, at 1490 Lombard Street (later The Bijou Cafe, also run by Larry Magid)

A newspaper ad for the second Quaker City Rock Festival at The Spectrum, on December 6, 1968. The Grateful Dead were billed along with four other West Coast groups

December 6, 1968 The Spectrum, Philadelphia, PA Sly And The Family Stone/Grateful Dead/Iron Butterfly/Steppenwolf/American Dream The 2nd Quaker City Rock Festival
The first event at The Spectrum was not a sports event, but a jazz festival. Herb Spivak regularly booked jazz acts at The Showboat, so Magid and the Spivaks promoted the First Quaker City Jazz Festival at The Spectrum on September 30, 1967. The next year, the Electric Factory promoted two Quaker City Rock Festivals. The naming conventions have confused matters a little bit, but the 1st Quaker City Rock Festival was on October 19, 1968, featuring Big Brother And The Holding Company, Moby Grape, The Chambers Brothers and Buddy Guy.

Seven weeks later, on December 6, the second Quaker City Rock Festival was held, with three bands from San Francisco and two from Los Angeles. Note that the Grateful Dead were the only one of those bands not receiving any radio play, and that all four other bands sold far more albums than the Dead ever did. Nothing is known of the Dead's performance. I assume they played a short, hour-long set or something similar.  Al Kooper was listed on the bill, but he was just the MC, announcing bands. I don't think he played with any of the groups, more's the pity. update: per below, Creedence canceled and was replaced by American Dream. Al Kooper sat in with the Dream.

[update] Another scholar weighs in with some further details in the Comments
At that time the venue had a revolving stage (until mid-'69), which bands hated. 
Al Kooper was the MC and played with American Dream, replacing Creedence Clearwater (who canceled). 
Some audience memories: "Stage was in center and rotated. Dead used own PA...so wouldn't let it rotate. Place wasn't full so they encouraged those sitting behind to come around... Sly and the Family Stone stole the night... [The Dead] were freaky and weird and that was alluring. Shows in 72 and 73 were transcendental: made me a Deadhead for life."
"There was a round stage in the middle of the floor of the Spectrum that rotated slowly. However the Dead didn't dig the rotating thing so they set up their own sound... One thing I do remember is Al Kooper being the MC but also sitting with a local band and jamming blues to fill in for Creedence who did not show up."
"Al Kooper covered Donovan's Season of the Witch with the Philly band American Dream who replaced CCR."
"We really had gone to see InDaGaddaDaVida by Iron Butterfly but I personally was awed by Sly and the Family Stone... The Dead played at a different stage while the other bands played 'In The Round'."
Al Kooper recalled that "Larry Magid, the promoter, paid me with a coffee table I had admired on a previous visit."
http://www.dead.net/show/december-6-1968 

Yet another update: regular Correspondent Jesse found a scan of a magazine ad by the Grateful Dead's booking agency

I am not sure what magazine this is from. The Millard Agency, run by Bill Graham, booked the Grateful Dead in late 1968. It may be an ad in an industry publication.

The Electric Factory made a brief foray into Baltimore in early 1969, promoting 3 concerts as "The Baltimore Rock Festival." The Grateful Dead opened for the Chambers Brothers for two shows at The Lyric Theater in 1969 (the amazing ad is via the Rock Concert Data Base)

February 9, 1969 Lyric Theater, Baltimore, MD: Chambers Brother/Grateful Dead (two shows)
For whatever reasons, Baltimore in the 1960s did not have many interesting touring rock bands perform in the city. Although this show date has long been known, nothing is known about the concerts themselves. Some recent research by other scholars (the Rock Concert Tour Database, via LIA at DeadEssays) has shown that the Dead's Baltimore date was a double show headlined by the Chambers Brothers, and promoted by The Electric Factory.

To my knowledge, the Factory's foray into Baltimore was not repeated, but this early date shows the interest in their efforts to expand beyond Philadelphia itself. If anyone knows anything about the Lyric shows, even 4th hand rumors, please mention them in the Comments.

February 14-15, 1969 Electric Factory, Philadelphia, PA; The Grateful Dead/Paul Pena
The Grateful Dead returned to the Electric Factory proper on the weekend of February 14-15. Presumably they were ok with the Electric Factory's accommodations, too, since they had already played Quaker City and Baltimore for them.

Paul Pena had an electric blues band that toured around a little. He was losing his eyesight due to a genetic condition. He met the Dead this weekend, and in 1971, when he was completely blind, he moved to the Bay Area. Jerry Garcia helped him get a recording contract with Fantasy Records, played on his records, and helped make sure that the Keystone Berkeley provided him with regular gigs, sometimes opening for Garcia and Saunders. Pena's song "Jet Airliner" ended up being a big hit for Steve Miller, and Pena was later the subject of a documentary, recounting how he taught himself the "throat singing" of Tuvan monks.

After February 1969, the Grateful Dead did not play Philadelphia again for 15 months, and they did not play for the Electric Factory for over 3 years. Nonetheless, Cutler and Scully were clear that the goal was to conquer Philadelphia and play the Spectrum. The peculiar structure of the Philadelphia market made it both an admirable goal for the band and a plan with no possible alternative.

By the Summer of 1970, it had become clear to the Electric Factory partners that the original venue at 22nd and Arch was too small for the exploding rock concert history. The partners could not afford to promote the most popular bands at any place save the Spectrum. At the same time, the original operators of the Spectrum were in serious financial trouble. While we tend to look back to the late 60s as a golden age of sports, that was not really true financially. The Philadelphia 76ers of the 1960s were a great team, featuring hometown legend Wilt Chamberlain (not to mention Hal Greer, Billy Cunningham and Chet Walker), but Wilt was traded to the Lakers in Summer 1968 for what were essentially financial reasons. Attendance, ticket prices, sponsorship and particularly Television deals for NBA and NHL teams were a tiny fraction of today's money, and thus the Spectrum, even in sports-mad Philly, went into bankruptcy in 1970.

The Spectrum went into receivership proceedings, and as part of the agreement to keep the venue open, Electric Factory agreed to produce at least 10 concerts per year, starting in 1970 or 71. In fact, the promoters rapidly exceeded that number, and in some years they produced as many as 60 rock concert events at the venue. If it had not been for the Electric Factory, the Spectrum may not have been a viable venue at all. It was a little-known fact that 70s-era arenas, without luxury boxes or high-end concessions, only broke even from sports tenants. Special events like rock concerts, ice shows and conventions provided the profit margin. So with Electric Factory dominating Philadelphia concert promotion and the biggest venue in town, they were instrumental in making the Spectrum thrive.

The Grateful Dead played an outdoor show in Philadelphia with Jimi Hendrix for the Concerts East production company. Sam Cutler described the event at length, and there was nothing good about what should have been a great event.

The Road To Broad Street
May 16, 1970 Football Stadium, Temple University, Philadelphia, PA: Jimi Hendrix Experience/Grateful Dead/Steve Miller Band/Cactus
Early in 1970, the Grateful Dead were pretty much playing any show that Sam Cutler could book for them, because the band needed the money. I'm sure the Electric Factory would have tried to book the Dead again, but the small venue downtown probably couldn't pay their fee. Thus the Dead played an outdoor concert booked by Concerts East, a national competitor to regional promoters like Bill Graham Presents and Electric Factory.

Concerts East and its counterpart Concerts West were affiliated with Jerry Weintraub, and they booked some of the biggest touring acts, including Elvis Presley and Jimi Hendrix. Later they became significant promoters of Led Zeppelin, starting in 1971. Because Concerts East was national rather than regional, they often used larger venues not typically used by the regional promoters, who usually controlled the local venues. The Temple University football stadium was small for a stadium, with a working capacity of about 20,000. Sam Cutler described this debacle of an event in some detail in his book You Can't Always Get What You Want. Without naming names, Cutler alludes to the fact that the promoters seemed to be associated with certain Connected Gentlemen, rather than righteous hippies. This is a common theme with stories about Concerts East and Concerts West.

Since the Dead played for a national competitor, it probably didn't sit well with the Electric Factory. On the other hand, the Dead never played for Concerts East or Concerts West again, to my knowledge, so that lesson seems to have been learned.

October 16, 1970 Irvine Auditorium, University of Pennsylvania, Philadelphia, PA: Grateful Dead
Back in May, when the Dead had opened for Hendrix at Temple, the band had not yet released Workingman's Dead, and were still sort of a hippie cult item. Once the album came out in June, however, the Dead had a greater footprint thanks to FM radio airplay. FM rock radio, known at the time as a "Free Form," "Underground" or "Progressive" format, to distinguish it from AM Top 40, had gotten its start in San Francisco at KMPX-fm, later moving to KSAN-fm. FM rock started to sweep the country. Philadelphia's big rock station was WMMR-fm (93.3), which started playing rock on April 29, 1968.

Once FM rock stations hit a city, bands like the Grateful Dead had a chance. If a dj liked the song, he played it, regardless of the length. Songs would become well-known, like Top 40, even though no single would have been released. Once Workingman's Dead came out, the Dead started to get regular play on stations like WMMR. So by the Fall of 1970, the Dead could return to Philadelphia as headliners. This specific concert was the Homecoming Dance for Drexel University, although using the auditorium at the nearby University of Pennsylvania.

Drexel would give up football in 1973, but it was still following the older tradition. Since Homecoming was a campus event, the Dead's fee would have been subsidized, and would not have to have been entirely covered by ticket sales. Every other row of seats were apparently reserved for Drexel alums and their dates (or spouses), and the rest sold to the general public. Apparently it was quite a peculiar scene, with every other row steadily emptying out.

November 22, 1970 Middlesex Community College, Edison, NJ: Grateful Dead/New Riders Of The Purple Sage
I have written about this event at length elsewhere, so I won't recap it. This was a Sunday night show at a suburban junior college, clearly subsidized by the school entertainment budget. Since the show was not advertised off campus, it did not conflict with any non-compete clause enforced by Bill Graham at Fillmore East. Edison is about equidistant from Philadelphia and New York. The robustness of the Philadelphia concert market was greatly enhanced by suburban New Jersey teenagers who often found it easier to go to Philly rather than New York Metro.

The Grateful Dead played around the Philadelphia area in April 1971. Franklin & Marshall is in Lancaster, PA, about an hour West of Philadelphia. The Electric Factory seems to have participated in producing this show, and apparently many fans from Philly were there.

April 10, 1971 Mayser Center, Franklin & Marshall College, Lancaster, PA; Grateful Dead/New Riders Of The Purple Sage
The Grateful Dead began their assault at Franklin And Marshall College. F&M is a highly regarded liberal arts school with about 2000 students, about an hour west of Philadelphia, in the center of Amish country (the pretzels are great, trust me). The school would have been heavily populated with undergraduates from the Philadelphia area. This event, held in the gym, was actually the school's Senior Prom. You can read all the memories on the archive, but it sounds like it was some Prom. It was near enough to Philadelphia, however, that there were some non-students as well, no doubt drawn by hearing them on the radio. Much of the school probably got on the bus, and it sounds like some townies did, too.

The presence of fans from the Philadelphia area would be no surprise, since it appears that the Electric Factory played a part in promoting the show (this poster appears in Magid's book). So the Electric Factory had a good idea of how the Dead were building a market in the suburbs.

April 13, 1971 Catholic Youth Center, Scranton, PA: Grateful Dead/New Riders Of The Purple Sage
Scranton is two hours (125 miles) north of Philadelphia. The Dead did not play a college, as Scranton was an old industrial town that had seen better days. However, Scranton was just in striking distance of Philadelphia, so it would have fit Rock Scully's goal. Also, with nothing happening in Scranton, teenagers and young adults would be looking to get out, and that likely meant Philadelphia or New York, so any nascent Deadheads would have had plenty of future opportunities.

April 14, 1971 Christy Matthewson Stadium, Bucknell University, Lewisburg, PA; Grateful Dead/New Riders of The Purple Sage
Bucknell University is a private liberal arts college two and a half hours and 160 miles Northwest of Philadelphia. It may seem strange for the Dead to have continued their pursuit of the Spectrum so far from Philadelphia, but Rock Scully's prescient understanding of the FM rock market starts to make sense. By Spring 1971, the Dead had released American Beauty, and the band's music was in high rotation on every FM rock station. The Dead toured mostly colleges in Spring 1971, and FM had primed the pump. All the undergraduates were ready for Fillmore East bands, and the Dead were the real deal. It seems that every undergraduate who same them on the East Coast that tour is still on the bus today.

Lewisburg is no metropolis, so many if not most of the undergraduates would have come from Philadelphia (or Pittsburgh), and would have heard the Dead on WMMR. There can't have been much to do in Bucknell, so when Spring came and a real rock band was coming, all those Philadelphia teenagers were going to go. The campus radio station probably hyped the show, too, and their may have been no other FM station playing rock out there at the time.

Christy Mathhewson--Memorial Stadium was a 13,100 seat stadium built in 1924. Matthewson was a Bucknell alumnus who was a Hall Of Fame pitcher for the New York Giants. In tiny Lewisburg, any student or townie who wanted a ticket would have gotten one. The high of the day was 60 degrees, 10 above the average, so it would have been a great spring day. Now, a commenter on the archive says

I was at this show. Garcia played with the New Riders from 8:15 until 10:30. The Dead came on at 11:00 and were still playing when we left at 3:30. I've seen Garcia, the Dead and and Weir and Lesh many times since then, but I have to say this is the best Dead show I was to. The show is wonderful but heck I was there so take anything I say with a grain of salt Cause I was 16.
Sparsely attended (300-400?).

Even though I think fans usually underestimate sparse crowds, it still wasn't a huge audience.  But I'm certain they all returned to the dorm as permanent Deadheads, and thus the legend would have gotten back to the Philadelphia suburbs.

April 15, 1971 Allegheny College, Meadville, PA: Grateful Dead/New Riders of The Purple Sage
Allegheny College was an even smaller school (2000 students) than Bucknell, and nearer to Pittsburgh and Cleveland than Philadelphia. Nonetheless, it would have had its share of students from greater Philadelphia, so word would have filtered back come the Summer. Meadville is pretty isolated, and at least one archive commenter recalls the scene

This show was a blast and is captured beautifully here. A very intimate setting, and a crowd that was primed and gliding with the scene. I was there (as Lou Sleaves) with a group of friends, some from Virginia - Buckeyes, Dick (AKA Bones), Helmet Head, meableffutS, Cliff, Kiff, Madman, Carl. We brought a shopping bag full of oranges and threw them around in the crowd in that small, old gym. The Dead were very friendly and had a running conversation wih the crowd, not separated from them by more than a few feet. The atmosphere was bright, upbeat, trippy.

April 17, 1971 Dillon Gymnasium, Princeton, NJ:Grateful Dead/New Riders of The Purple Sage
I have also written at length about this legendary show, so I needn't recap it. Almost every single person attending the show was a Princeton student, and Princeton students are from everywhere. Thus although the future leaders of American all became Deadheads that night, they were spread far and wide. Princeton is only about an hour Northeast of Philadelphia, however, so word would have filtered back in the Summer about how you could buy the Brooklyn Bridge for a dollar and a quarter.

In the space of a week in April 1971, the Grateful Dead had played five shows, West, Northwest, North and East of Philadelphia. Save for Scranton, undergraduates abounded, and many of those young adults would return to Philadelphia in the Summers and possibly for careers. If the Dead came to Philadelphia, all of them were going to the show, and they were taking their brother, their roommate and their girlfriend. Rock and Sam knew what they were doing: FM radio had piqued student interest, and there's nothing like the legend of five hour concerts as a permanent--if fuzzy--memory of glorious undergraduate days.

The Spectrum in Philadelphia in 1991, right next to Veterans Stadium

September 21, 1972 The Spectrum, Philadelphia, PA; Grateful Dead
John Scher had booked the Grateful Dead in Jersey City on July 18, 1972, and demonstrated that the band was a viable draw, even without any sort of real hit. By this time, the Dead had put out yet another popular album ("Skull And Roses"), and both Garcia and Ace were getting FM airplay. However, although the Dead had greatly expanded their market in Fall 1971 by allowing their shows to be broadcast live on FM radio, there had been on broadcast in Philadelphia because their had been no gigs there. Nevertheless, with a return visit to Jersey City on September 19, and plenty of eager undergraduates ready to hear the Dead again, the band finally played Philadelphia's biggest venue on September 21, 1972.

Although the Spectrum had a concert capacity of 15,000-plus, the Electric Factory had arrangements were the building could be configured for a smaller crowd. The nature of rock at the time was that sold-out shows were as important as ticket sales, so if an act could only sell 8000 tickets, it was better to configure the arena for 7500 and have a sell-out, rather than try and sell 8500 tickets and leave the arena partially empty. So it's possible that the Electric Factory configured the Spectrum this night for a somewhat smaller crowd, perhaps 10-12,000, and they wouldn't have explicitly advertised it. Also, both the Philadelphia and Jersey City shows would have drawn from the same New Jersey suburbs, and their may have been concerns about how many tickets were sold.

Nonetheless, Sam and Rock's strategy had worked, and the Dead were booked at Philadelphia's biggest venue. And we don't have to ask about ticket sales--the Dead were booked at the Spectrum just six months later, and I guarantee you that the house was configured for the max in the spring.
[update] LIA found a newspaper review that said The Spectrum was packed to capacity.

March 24, 1973 The Spectrum, Philadelphia, PA; Grateful Dead
The Dead had played a killer show in September, but all the evidence suggests that the March '73 show was even better. The archive is full of vague, delirious memories of when Giants walked the Earth. The Dead owned the Spectrum now.

The Electric Factory promoted the legendary two-day Allmans/Dead show at RFK stadium in Washington, DC

June 9-10, 1973 RFK Memorial Stadium, Washington, DC: Allman Brothers Band/Grateful Dead/Doug Sahm Band (9th)/Wet Willie (10th)
The Summer of 73 began for the Grateful Dead with two huge stadium concerts with the Allman Brothers in Washington, DC. There was no major concert promoter in the DC/Baltimore area, so the shows were promoted by The Electric Factory. The Allman Brothers Band were the most popular touring act in the country, behind "Ramblin' Man" and the Brothers And Sisters album, but the RFK concerts showed that if the Dead were booked with the Allmans, attendance escalated beyond the individual appeal of both bands.

Both shows were epic, and very well attended, and their success led directly to the indescribably huge event at Watkins Glen. The second night ended with a great jam, when members of the Allmans joined the Dead. The Grateful Dead and the Electric Factory were good to go, and Philadelphia was there for the taking.

However, Magid describes an event that probably took place at RFK that indicated trouble ahead:

Before a Grateful Dead concert at JFK Stadium [sic--I am assuming it was RFK, as the Dead never played JFK until the 80s] in the seventies, a roadie setting up the show demanded to be supplied with cocaine. Allen [Spivak] refused. The roadie and his crew stopped working, a standoff that lasted four or five hours. Finally, Allen decided to give them a $5000 down payment on their night's work, and that did the trick [p.33]

This sort of crew behavior would cause the Dead serious problems when they returned to The Spectrum in a few months.

September 20-21, 1973 The Spectrum, Philadelphia, PA; Grateful Dead
After a triumphant summer, including the Watkins Glen show (July 28) and two outdoor shows in Jersey City with The Band (July 31-August 1), the Grateful Dead returned for two shows at the Spectrum. They owned Philadelphia now.

After a falling out with the Electric Factory, the Grateful Dead played two shows for a different Philadelphia promoter at the smaller, older Philadelphia Convention Center.

August 4-5, 1974 Philadelphia Convention Center, Philadelphia, PA: Grateful Dead
If the Grateful Dead owned Philadelphia after 1973, and had made huge returns for the Electric Factory promoters, why then did the band play at the much smaller and older Philadelphia Convention Center the next year, for other promoters entirely? Something had to have gone wrong.

McNally explains what took place:

The distrust for promoters was epitomized in a 1973 incident between crew member Ben Haller and Philadelphia [Electric Factory] promoter Allen Spivak. Miffed because the crew had been served spaghetti--the Dead's contract called for high-protein dishes like steak and lobster--Haller collected leftovers from his, Lesh's and Ramrods' plates and proceeded to dump them on Spivak's head. Larry Magid, Spivak's partner, wrote to road manager Sam Cutler to complain

...we've had quite a few problems with your crew in the past. You say that the band knows that they're animals but that you can't do anything about the situation. All well and good, but they do represent you.

Cutler replied

In the years to come, no doubt, we'll all be able to laugh about it, but until then I guess it will be hard for the Dead tIo work with you and Allen....allow me to finish with the conclusion that the Dead made their own bed, and thereafter they lie in it.

That they did; for the next three years they worked with another Philadelphia promoter at a much smaller venue, costing themselves a considerable amount of money. (McNally p.268)

The Dead had Philadelphia, a huge rock market, under their control, and they let it slip away because of crew misbehavior. The Electric Factory so dominated Philadelphia concerts--later a subject of a major Federal anti-trust lawsuit--that the band was left with no alternative but to take less money at a smaller place. The Philadelphia Convention Center was at 3400 Civic Center Boulevard, and it was built in 1931. It's concert capacity was probably about 12,000, which at most was just 80% if Spectrum capacity.

The Tower Theatre in Upper Darby, PA, in suburban Philadelphia.

November 16, 1974 Tower Theatre, Upper Darby, PA: Jerry Garcia & Merl Saunders (early and late shows)
The Grateful Dead had stopped touring in October 1974, and one reason was apparently to rid themselves of reckless crew members. Only the Dead would go about managing personnel issues in such a backwards way. In any case, Jerry Garcia and Bob Weir immediately started performing, within weeks of the Dead's "Last Five Nights" shows at Winterland (Oct 16-20, 1974). Garcia was the first to tour the East, with his club band featuring Merl Saunders.

Obviously, Garcia/Saunders were not going to play the Spectrum. The Tower Theatre was in the Philadelphia suburb of Upper Darby, and had a capacity of about 2000. Another smaller, local promoter booked the shows.

April 11, 1975 Tower Theatre, Upper Darby, PA: Legion Of Mary (early and late shows)
Garcia/Saunders returned the next spring, as The Legion Of Mary, so obviously the Fall shows had worked out well.

October 31, 1975 Tower Theatre, Upper Darby, PA: Jerry Garcia Band with Nicky Hopkins (early and late shows)
The newly minted Jerry Garcia Band returned in the Fall for double shows. Once again, they weren't going to play the Spectrum in any case, but it never helps matters to have poisoned relations with the biggest promoter in a town.

June 21-24, 1976 Tower Theatre, Upper Darby, PA: The Grateful Dead
The Dead were fortunate that events conspired to make some peace with the Electric Factory. The promoter using the Tower Theatre elected not to continue, and The Electric Factory took over the venue by the end of 1975. This gave Electric Factory a different sort of venue for acts not suitable for the Spectrum.

The Grateful Dead had returned to touring in June 1976. They were supporting a turkey of an album, Steal Your Face, so they elected to make the first tour an event rather than focus on a big moneymaker. After two stealthy warmup shows in Portland, OR, the Dead played multiple nights in small theaters in five cities that were Dead strongholds, booked by long-standing Dead promoters. The tickets were only available to people on the Grateful Dead mailing list, an unprecedented approach in the 70s. All the shows sold out instantly. The last night in each city was broadcast on FM radio.

The Grateful Dead played four nights at the Tower Theatre on June 21-24, 1976, which was now booked by the Electric Factory. The final night (June 24) was broadcast live on WMMR-fm, the first Dead broadcast in the Philadelphia area. Although not as profitable as a Spectrum show might have been, the Dead's return was a prestigious booking for The Electric Factory. Also, the Dead played from Monday to Thursday, nights when the Tower would typically have been dark. Thus the sold-out shows were like free money to the Electric Factory, since any regular weekend booking could still take place.

April 22, 1977 The Spectrum, Philadelphia, PA: Grateful Dead
Come the Spring, and things were back to normal for the Dead in Philadelphia. The Dead headlined the Spectrum. They would headline the venerable arena 47 more times. Jerry Garcia would come back and play the Tower Theatre 9 more times, and even played the Spectrum four times (JGB Mar 16 '78, possibly with a smaller configuration, JGB and Weir/Wasserman Nov 3 '89, JGB Nov 12 '91 and JGB Nov 16 '93). After 1976, the crew was less notorious, and seems to have caused no new problems.

Bands need promoters, but promoters need bands, too. While it is true that the Dead's crew cost them some real money in Philadelphia in 1974, the fact was that the enormous drawing power of the Dead was such that The Electric Factory needed the Grateful Dead, just as they needed the Electric Factory. Electric Factory remained, and remains, the dominant promoter in the Philadelphia area, a fact confirmed by a Federal anti-trust lawsuit against them in the 21st century.

Rock Scully had a plan. For all his tall tales and personal excesses, he was right as rain about how FM radio was going to work in 1970, long before most band managers had figured it out. The road to the Philadelphia Spectrum wasn't exit 17 on I-95, but rather through Lancaster, Scranton, Lewisburg and Meadville. That roundabout road kept them on stage at the Spectrum long after their peers had stopped working, and the Grateful Dead ruled Philadelphia right up to the end.