Iron Mountain is a mountain in the San Gabriel Mountains of Los Angeles County, California. Sometimes referenced as Iron Mountain #1 or Big Iron, the 8,007 ft (2,441 m) peak was originally called Sheep Mountain by the early miners in San Gabriel Canyon because of the large bands of bighorn sheep that roamed the slopes. The United States Geological Survey, which mapped the San Gabriels in the 1890s, ignored the local designation and gave it its present name.