The Lettes were started in 1936 and were then called the "Caterpillar Girls" because the team was sponsored by and composed of women from Caterpillar Tractor Company in nearby East Peoria. They became the Caterpillar Dieselettes in 1940, the Sunnyland Lettes in 1956, and the Pekin Lettes in 1959. In the late 1950s and early 1960s the Lettes average attendance-per-season was over 100,000, with thousands of spectators attending each game. The 1963 season averaged over 5,000 fans per game, setting a national ASA attendance record of 122,000 for 21 home games. In 2005, the Pekin Lettes team was inducted into the ASA Hall of Fame.