About the best comparison you could make is with the University of Montana and Montana State University.
State of Montana:
Population in 2000: 902,195
Largest city: Billings population 89,847
University of Montana:
Enrollment: 13,961 total fall 2006
Missoulla population: ~60,000
Stadium capacity: 23,183
Montana State:
Enrollment: 12,338 total fall 2006
Bozeman population: ~50,000
Stadium capacity: 15,000
UM will be adding a second level to their stadium for this next coming season that will bring their total capacity to over 25,000. MSU also has plans to add seating and finish enclosing one endzone of their stadium but no official plans have been announced.