One of the critical differences between NFL and college stadiums is their longevity. Upon reaching middle age, cities demolish and replace NFL stadiums, while colleges typically remodel their stadiums. The second difference in days gone by was that NFL teams commonly played in stadiums built for baseball. Most college stadiums were purpose-built for football, perhaps having a running track.
Today's Tidbit... NFL and College Football Stadiums in 1956
This is a great find!