On the left, north of the Tiburon Wye on 101 is a hill where horses often graze. The Marin County Open Space District owns Horse Hill Open Space Preserve, 55 acres of fenced pasture. The Alto Bowl Horseowners’ Association (ABHA) is responsible for managing the fourteen horses permitted to graze on Horse Hill. ABHA is also responsible for all equestrian facilities: shelters, corrals, hitch rails, manure bunker, fences and other horse-related improvements. ABHA volunteers work with County Parks, school groups and volunteers in waging an ongoing battle against French and Scotch broom and other invasive, exotic plants. In 1961, a developer proposed to build 900 homes in the area. The saga of preserving Horse Hill covers three decades. The first step was to form the Alto-Sutton Manor District Association. Both the Alto community in the county and the Sutton Manor community in the city of Mill Valley are at the base of Horse Hill. The next step was to launch the recall of a pro-development county supervisor. The result was the first such successful recall in California. From then on it was one challenge after another involving city, county and state agencies, fund raising, developers, legal action, eminent domain action, lobbying, public relations and even MMWD that had announced plans to build a water tank on Horse Hill.