The California ProKart Challenge hosted the penultimate round of the 2021 season on the September 11-12 weekend at the Willow Springs International Raceway. The Rosamond, California facility has been the site of many Superkarts! USA regional program events in the past, including both the famed Streets of Willow course and the karting circuit. The two-day event for Round Five of the 2021 championship program was held on the nine-turn, 6/10-mile kart track in the counter-clockwise direction.

The ProKart Challenge returned trackside on June 12-14 with the second and third rounds contested on the kart track at the Willow Springs International Raceway. Racing for Superkarts! USA had been shut down since the March weekend of the SKUSA Pro Tour WinterNationals in New Orleans, but welcomed triple-digit numbers for each of the two rounds of regional racing program under almost-perfect weather conditions at in Rosamond, California. Attendees followed social distancing guidelines to help keep officials and competitors safe while enjoying the three-day event.