The University of Illinois - Champaign Urbana had I think, 21 NPCs at one point. It looks like it have shrunk to 19.
http://www.uiuc.edu/ro/panhellenic/
I think your school, or U of Illinois is the closest that anyone's ever gotten to having all 26 NPCs, but no campus has ever done it, to the best of my knowledge....
xp2k, I think you will find
many campuses that do have all 4 of the NPHC sororities present on campus....having all 26 of the NPC is another story!
