The 25 Hours of Thunderhill is an endurance racing event held annually during the first weekend in December in Northern California, at the Thunderhill Raceway Park; just outside the small city of Willows. The race is longest road event on a closed course in the United States.

It has been run since 2003,^[1] sanctioned by the National Auto Sport Association.^[2] It is the successor to the Timex 12 Hours of Thunderhill event run between 1998 and 2002.^[3]

References

^ "25 Hours of Thunderhill – Past Results". nasa25hour.com. Retrieved 22 February 2017.
^ "Davidson Racing Norma wins the 25 Hours of Thunderhill". Motorsport.com. 2014-12-07. Retrieved 22 February 2017.
^ "History of the 25 Hours of Thunderhill" (PDF). NASA 25 HOURS OF THUNDERHILL. nasa25hour.com. Retrieved 22 February 2017.

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Other	25 Hours of Spa 25 Hours of Thunderhill Carrera Panamericana Charge of the Headlight Brigade Targa Florio TCR Spa 500 Laps or 23 Hours The 2904
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