Complex sentence: In 1900 Heisman, then "the undisputed master of Southern football", went to Clemson University, where he coached four winning seasons and three Southern Intercollegiate Athletic Association (SIAA) titles.
Split into simpler sentences: In 1900 Heisman, then "the undisputed master of Southern football", was hired by Clemson University. Heisman would lead Clemson to four winning seasons and three Southern Intercollegiate Athletic Association (SIAA) titles.