Horse Flats is a region of the San Gabriel Mountains in the Angeles National Forest north of Los Angeles. It is known for its US Forest Service campground (open April 1-November 15) and for the excellent granite bouldering near the campground. It is off California State Route 2. The elevation is . Closed in the winter months. In the campground is Mount Hillyer Trail, which connects to the Silver Moccasin Trail. History In the nineteenth century, the area was used by Tiburcio Vásquez and his gang as a hideout and corral for their stolen livestock References External links Horse Flats Bouldering website Horse Flats campground Climbing Info Climbing areas of California Landmarks in Los Angeles San Gabriel Mountains