The NASA 25 Hours of Thunderhill is the longest closed-course endurance race in North America. Begun in 1998 as the Timex 12 Hours of Thunderhill, the race expanded to 25 hours in 2003, and has since evolved to become known as one of the most grueling endurance races in the nation, attracting amateur and professional sports car drivers from around the world. From the challenging track and the winter weather to the speed differentials among all the cars involved, nothing about the 25 Hours of Thunderhill is easy. Come and support Eastern Racing at the NASA 25 Hours of Thunderhill!