Iron Mountain, Mountain summit in San Gabriel Mountains National Monument, California, United States.

Iron Mountain is an 8,007 ft (2,441 m) peak in the San Gabriel Mountains of Los Angeles County, within the Sheep Mountain Wilderness of the San Gabriel Mountains National Monument. It has no maintained trails and no facilities; the climb gains about 6,000 vertical feet over loose soil, decomposed rock and brush, with some routes requiring rock-climbing skill.

The San Gabriel Mountains were managed by the US Forest Service for decades before the area was designated a National Monument in 2014. That decision placed the peak and its surroundings under stronger protection than before.

Early miners in San Gabriel Canyon called the peak Sheep Mountain for the large bands of bighorn sheep that roamed its slopes. The United States Geological Survey, mapping the range in the 1890s, set aside that local name and gave the mountain its present one. Will Thrall recorded a 1940 Forest Service plan to restore the Sheep Mountain name, which was never carried out; the Sheep Mountain Wilderness now keeps the old name alive.

Starting the hike early in the morning is a good idea, as the upper part of the trail offers little shade and temperatures can rise quickly. Sturdy footwear is necessary on the rocky terrain, and carrying enough water is essential.

On a clear day, the summit offers a view toward both the Mojave Desert and the Los Angeles Basin at the same time, two very different landscapes visible from one spot. This rare vantage point is something many visitors do not expect to find at the top.