The split between "I-A" and "I-AA" is relatively recent. Prior to 1973, there were only two divisions: "major-college" (which became Division I) and "college-division" (which became Divisions II and III). In 1978, Division I was split into I-A and I-AA. (Note that the split in Division I is for football only; in all other sports Division I is a single entity.)
The intent with this database is to include all teams that were ever considered to be in the "top" division that existed at the time. All years' data will be entered, but only data earned in the top division will count in the winning percentage calculations.