While roller derby has its origins in the banked-track roller-skating marathons of the 1930s, Leo Seltzer and Damon Runyon are credited with evolving the sport to its competitive form. Professional roller derby quickly became popular; in 1940, more than 5 million spectators watched in about 50 American cities. In the ensuing decades, however, it predominantly became a form of sports entertainment, where theatrical elements overshadowed athleticism. Gratuitous showmanship largely ended with the sport’s grassroots revival in the first decade of the 21st century. Although roller derby retains some sports entertainment qualities such as player pseudonyms and colorful uniforms, it has abandoned scripted bouts with predetermined winners.