If you're looking for big in terms of numbers of NPC chapters (I have included ones that have 8 or more)...
Penn State- 20
Maryland- 14
Syracuse- 12
Cornell- 11
IUP- 11
Pitt- 11
GWU- 10
Villanova- 9
Delaware-9
URI- 9
Towson- 8 (and open for extension)
Boston U- 8
Lehigh- 8
UPenn- 8
Another school that doesn't have as many NPCs, but a very strong Greek presence is Bucknell. They have 6 NPCs, plus ADPi to colonize shortly. About half (or maybe more) of the students are Greek, but they have to wait until fall of their sophomore year to join.
It should be noted that a large number of chapters doesn't necessarily mean that a large number of students are Greek or that the chapters are large or that the administration or non-Greeks are supportive of the community. However, a large number of chapters is generally indicative of diversity and provides PNMs with more places to find a home.
I can answer any questions you have about Maryland (and there are several other Terps on GC too). Maryland is a little over 10% Greek, and chapters are about 110-120ish after spring recruitment. The sororities all have houses, with 3 of them recently renovated and 2 more about to undergo renovations. Chapters at Maryland are often among the best (award-winning, high achieving) in their National Organizations, because the Office of Fraterntiy and Sorority Life (OFSL) expects a lot from its chapters. In other words, OFSL requires things that many of our National Organizations challenge us to do in areas of programming, leadership, scholarship, recruitment, philanthropy, etc. I never felt like Maryland was particularly anti-Greek; I think the general student body is fairly neutral. There was always a small, but vocal minority that is anti-Greek, but I imagine that happens at even SEC schools.
GWU's Greek community is particularly fast-growing. They have added Alpha Phi, Pi Beta Phi, and Chi Omega within the last 7 years.
Penn State's Greeks are very spirited (as is the whole school). THON is a huge deal, and Greeks are very involved in the fundraising. "As just over 10 percent of the student population, Greeks raised roughly 40 percent of the total money donated to THON."
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