Red Mountain, formerly known as Osdick, is an unincorporated community in San Bernardino County, California, United States. Red Mountain was established in 1919 as Osdick, a silver mine boom town Red Mountain is 32 mi south-southwest of Trona, part of the mining district of Randsburg, California and Johannesburg, California. Red Mountain has a post office with ZIP code 93558. The post office opened under the name Osdick in 1922 and changed its name to Red Mountain in 1929. In 2022, the community received a $1.5 million grant to clean sediment of arsenic from historic gold and silver mining from the kelly mine complex.