Mountain Spring is a spring in the Jacumba Mountains of Imperial County, California, near the head of In-Ko-Pah Gorge and the source of Myer Creek at an elevation of 2,323 feet. Beginning in 1863, it supplied water to the Mountain Spring Stage Station on the road between San Diego and Yuma, Arizona. Its importance lay in providing a dependable water source along a dry, rugged route, helping determine where travelers could stop and how overland travel through this difficult landscape was organized.