I was actually thinking of University of Michigan which has somewhere between 80,000 and 100,000 students.
In fact I wasn’t really thinking about number of students so much as I was campus size and number of buildings etc.
Not per the University of Michgan’s own enrollment numbers (PDF)
http://www.ro.umich.edu/report/11enrollmentoverview.pdf
For campus size, looks like Berry College has them beat. About 1800 students packed into over 26,000 acres.