Complex sentence: It would not be until seventy years later in 1959 that the first fraternities and sororities arrived on campus and not until the 1970s when they were recognized as national fraterntites and sororites.
Split into simpler sentences: It would not be until seventy years later in 1959 that the first fraternities and sororities arrived on campus. It was not until the 1970s when they were first recognized as national fraterntites and sororites.