From the Willow Springs International Motor Sports Park website:
Willow Springs International Motor Sports Park is a 600-acre complex of six racetracks embracing nearly every conceivable motor sports discipline. The park is located about an hour north of Los Angeles, California near Lancaster.The original track at the facility, Willow Springs International Raceway, celebrates its 50th birthday this year, and is steeped in historical significance. Construction of the track began in 1952, with the inaugural event held on November 23, 1953.