Original: Though founded in 1887, under Jack Hyles' leadership from 1959 2001 it became one of the megachurches in the United States and during the 1970s had the highest Sunday school attendance of any church in the world.
Simplified: It was under Jack Hyles' leadership from 1959-2001 that it became a megachurch, one of the first in the United States, with a steady weekly attendance of around 20,000.