It really depends on your definition. Some define the modern era as the widespread use of the two platoon system (1960's). Others, like me, define it to coincide with integration and the impact on the physicality of teams. Others, define it as 1973 when the NCAA divided itself into Division 1, Division 2, and Division 3.
To me, it doesn't matter which one you use as long as the comparisons are consistent. I seldom use, for examples, statistics prior to 1970 because the game, the money, the players ... are vastly different.