Two Established Chapters in One City...

[TCV]

I thought it was interesting how a glo has established two chapters in one city. For example, Alpha Sigma Alpha has two established chapters in San Antonio, TX.; Delta Upsilon in UT-San Antonio and Zeta Sigma in University of The Incarnate Word (although I don't know how far apart their establishments were).
That is the only glo I can think of. Do other glo's have a "twin" chapter in the same city? Is this common, if so why would a glo do that if it has already established their presence. I wonder if this would be double work for the Alumnae chapter supporting two collegiate chapters at once.
Any response on this would be insightful

~TCV