Marl Spring, in the northeastern Marl Mountains of San Bernardino County, California, was a crucial water source in the eastern Mojave, where dependable springs determined travel. It lay first along the Mohave Trail and later the Old Spanish Trail, continuing in importance after the Mojave Road was established in 1858 during the Mohave War. About 70 miles west of Fort Mohave, with the next reliable water 18 miles east at Government Holes and 30 miles west at Soda Springs, it was a vital stopping place for travelers crossing this desert stretch. The U.S. Army established Camp Marl Springs there in 1867 as an outpost of Camp Cady, and it remained in use until 1868.