The land on which the base now stands was originally known as San Jacinto Hot Springs. It was first developed in the late 19th century by Sidney Branch of Riverside. He built the Relief Springs Hotel there in 1888. In 1890, Branch bought a parcel of land north of San Jacinto on which were natural hot springs that had been known to local Native Americans for centuries. He developed it into a resort called Relief Hot Springs before selling it in 1913 to the three Gilman brothers – W. Earl, Grant and Forest Gilman.