Mountain Pass, California, is an unincorporated community in San Bernardino County near the Nevada border along Interstate 15. It lies on the south flank of the Clark Mountain Range at about 4,730 feet in elevation. Before its transformation into a rare earth mining hub, Mountain Pass was part of a high desert rangeland used for cattle grazing and seasonal travel.
In the late 1800s, ranchers from Ivanpah and the Mojave River region grazed cattle along the area’s sparse grasslands and natural springs. By the early 1900s, a few homesteads, corrals, and line camps appeared, but permanent settlement was limited due to aridity and isolation. The nearest centers of activity were Cima and Ivanpah, tied to the Union Pacific line.
During the 1920s and 1930s, open-range ranching declined as highway construction and mineral exploration expanded. U.S. Highway 91, built through Mountain Pass in the 1930s, connected Barstow and Las Vegas and reshaped movement across the desert. Prospectors began testing local outcrops for copper, fluorspar, and uranium.
In 1949, while searching for uranium, geologists discovered bastnasite—a mineral rich in rare earth elements. By 1952, Mountain Pass Mine was in production, marking the shift from ranching to mineral extraction. The mine’s bastnasite ore, containing about 7% rare-earth oxides, proved exceptionally rich. Throughout the 1960s, 1970s, and 1980s, Mountain Pass supplied most of the world’s rare earth elements, which are critical for electronics and defense.
Environmental concerns and global competition, particularly from China, led to a decline in the 1990s. A series of wastewater pipeline spills and stricter regulations led to the closure in 2002. Molycorp reopened the site in 2010 but went bankrupt in 2015. MP Materials acquired it in 2017 and restarted production, now emphasizing on-site recycling and domestic refining. Mountain Pass currently produces 10–15 percent of global rare earth supply and remains the only major U.S. operation of its kind.
Timeline:
Late 1800s – Early cattle grazing begins between the Clark and Mescal Ranges.
1890s–1910s – Small ranchers and homesteaders establish corrals and wells near Cima and Ivanpah.
1920s – Ranching continues; U.S. Highway 91 construction increases access.
1930s–1940s – Grazing declines; mineral prospecting grows.
1949 – Bastnasite discovered while prospecting for uranium.
1952 – Mountain Pass Mine begins rare earth production.
1960s–1980s – Peak years; mine supplies most of the world’s rare earth elements.
1980s–1990s – Environmental issues and foreign competition led to a decline.
2002 – Mine ceases operations.
2010 – Molycorp reopens the mine.
2015 – Molycorp declares bankruptcy.
2017 – MP Materials resumes production.
2020s – Expansion of domestic processing and magnet manufacturing.
Mountain Pass stands as a symbol of changing desert economies—from open-range cattle country to strategic mineral industry—each era leaving its own traces: windmills, corrals, and open pits scattered across the Mojave’s high desert plain.