According to John Robinson, author of Trails of the Angeles, "8007 foot Iron Mountain is by far the least accessible peak in the San Gabriels....No trail approaches its isolated summit , and to climb it you must start miles away and thousands of feet below." In this local hiking legend's view, "Big Iron" is the most strenuous one-summit hike in the entire San Gabriel range.
Originally, local miners in San Gabriel Canyon referred to the mountain as Sheep Mountain, descriptive of the herds of Bighorn sheep that once roamed its slopes. However, the U.S. Geological Survey, which mapped the San Gabriel Mountains in the 1890's, was apparently not as impressed with the fauna that roamed the surface of the mountain as it was with what lay beneath the surface, iron ore deposits. Thus the present name was bestowed. But the Bighorn were not entirely forgotten for the designated wilderness area where Big Iron is located is named "Sheep Mountain Wilderness."
The most common route to the summit is via the Heaton Flat Trail and then Iron's south ridge. See Heaton Flat Trail and South Ridge Route for a detailed description. A round trip by this route is about 14 miles with a humbling 7,200 feet of elevation gain.