The Marin County 100 Miler is a 104-mile clockwise loop in Marin County, California that links up many of the iconic trails and landmarks in the northern San Francisco Bay Area.  The route starts and finishes at Tennessee Valley Trailhead in the Marin Headlands (Golden Gate National Recreation Area) and totals out with 24,560 ft of gain.  It summits the highest points in Marin including Bolinas Ridge, Pine Mountain, Loma Alta, Big Rock Ridge and Mt.

Starting at the Fort Pierce Inlet, this route crosses the drawbridge in town leading you back onto mainland before crossing another causeway bridge over the Indian River back to A1A. Traveling down the remote Hutchinson Island with limited beach access water refill points, you can enjoy the waterfront views of the river for miles. Crossing the Frank A Wacha Bridge into historic Jensen Beach along Indian River Drive. Over the last causeway, you will hit Stuart Beach and road A1A back to Jensen Beach Park finishing on the beach.