### Instruction:
How many national championships had Youngstown State Penguins football team won prior to 1991?

### Input:
The 1991 Youngstown State Penguins football team represented Youngstown State University in the 1991 NCAA Division I-AA football season. The Penguins were led by sixth-year head coach Jim Tressel and played their home games at Stambaugh Stadium. They finished the season 12–3. They received an at-large bid to the I-AA playoffs, where they defeated Villanova, Nevada, and Samford to advance to the National Championship Game, where they defeated Marshall. This was their first national championship in school history.

### Response:
None. 1991 was their first national championship in school history so there weren't any prior national championships for Youngstown State Penguins football team.