Thunderhill Raceway Park is a road racing course located 7 miles (11 km) West of Willows, California on Hwy 162. The course is a fast series of twists and turns with minor elevation changes. Thunderhill is owned and operated by the San Francisco Region of the SCCA. It is host to many motorports events for cars and motorcycles. The SCCA uses Thunderhill for its automotive race competitions. The Northern California Chapter of the AFM runs several motorcycle races there every year. The standard road course at Thunderhill Park is a 3.0-mile (4.83-km), 15 turn course, however the track is configurable and event organizers can configure the course as they see fit. Thunderhill is the site of the longest automobile race in the United States; the 25 Hours of Thunderhill. The race is held annually during the first weekend in December and is sanctioned by NASA (National Auto Sport Association).