This is interesting. National college football champions going back to 1869 =>
https://www.sports-reference.com/cfb/years/index.html
Hmm....doesn’t include the following:
Navy has won one College Football National Championship in 1926 according to the Boand and Houlgate poll systems. The 1910 team also was undefeated and unscored upon (the lone tie being a 0-0 tie).
Even “back in the day” there was disagreement among the polls, ranking systems, etc