The Quad Dipsea is a 28.4-mile (45.7 km) trail ultra, held annually in November on the Saturday following Thanksgiving. The Quad starts and finishes in Mill Valley, following the Dipsea Trail westward to Stinson Beach, out-and-back twice over the same course as the Dipsea Race and the Double Dipsea. The race has 9,276 feet (2,827 m) of both climb and descent. First held in 1983 with only 8 runners, the race is now limited to about 250 runners.
The 28th Quad Dipsea, is scheduled for November 26, 2011