Subscribe to The Chicago Manual of Style Online
Q. How would the University of Chicago Press render the names of universities with multiple campuses?
A. As a copyeditor, I allow either a comma, an en dash, “at,” or nothing—but only after looking at what the university in question seems to favor (all universities have an internet presence these days) and then taking into account, if necessary, questions of consistency within the document or book or publication that I’m editing.
University of Wisconsin–Madison (that seems to be what they favor, and an en dash looks elegant here)
Indiana University South Bend (that’s how they do it)
University of California, Berkeley (that’s how they do it; remember to add a comma after “Berkeley” if the name occurs in midsentence)
A one-size-fits-all rule would be far easier to apply, but these days it’s pretty easy to find out the right answer.