That's a great article to see.
In my experience (as an alumna inside and outside Chicago), it has to do with dedication, as well as the very large pool of alumnae in the area. Since I live in the city proper, I'm a member of the Gamma Phi Beta Chicago Alumnae Chapter, as well as Chicago Alumnae Panhellenic. I know there are at least 3 other rather good-sized, active GPB Alum chapters in the suburbs, and I know the Alumnae Panhellenics are numerous and involved as well. The Chicago area is a GREAT place for greek alumni