Good NY Times article on the oldest trail race in the US.
Beautiful and challenging course requires both speed and skill. 2k feet of climbing in 7 miles.
The refined handicap system means any top age group runner can win (the top finishers each year are usually national age group champions).
It's known as the "Super Bowl of Marin" because of it's importance to the community, where winning a black shirt may be equal in status to winning the Nobel Prize.
https://www.nytimes.com/2018/06/13/sports/dipsea-trail-running.html