The 25 Hours of Thunderhill is an endurance racing event held annually during the first weekend in December in

Northern California Northern California (colloquially known as NorCal) is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California. Spanning the state's northernmost 48 counties, its main population centers incl ...

, at the

Thunderhill Raceway Park Thunderhill Raceway Park is a road racing, motorsports complex located 7 miles West of Willows, California, Willows, California, United States, in the Sacramento Valley. It is the venue for the longest automobile race in the United States, the ...

; just outside the small city of

Willows Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist so ...

. The race is longest road event on a closed course in the United States. It has been run since 2003, sanctioned by the

National Auto Sport Association The National Auto Sport Association (NASA) is an American motorsports organization promoting road racing and high-performance driver education. Founded in 1991, NASA hosts High Performance Driving Events (HPDE), automotive rallies, Time Trial ...

. It is the successor to the Timex 12 Hours of Thunderhill event run between 1998 and 2002.

References

{{Automobile endurance races Endurance motor racing