Folk music building trivia (Philadelphia area)

Today I am branching out on the subject of trivia questions.  It’s still related to a building, but this time the building is not a courthouse (or the house of a famous judge or lawyer). It’s a building where a coffee house hosted important concerts by folk (and rock) musicians back in the 1970s.  This is in what is to my mind a very posh suburb, though I do recall one of my friends from college mentioning that part of this town, where she went to college, was seedy. If someone said that to me now, I’d either start laughing or say something like, are you joking? But back then I just took it in and didn’t say anything. To get to the question, what coffee shop was in this building and why was it important?  I came across this when I was researching a folk artist I’m particularly interested in because he lived (and following his premature death was buried) near where I grew up.  I remember my seventh-grade English teacher who knew the man in passing, as I guess a lot of the “hippie element” around my hometown did, talking about his tragic death at a young age.  But while that man played in this coffee house, so did a great many others and some even better known. (It is in the Philadephia area.)