Marine Corps Base Camp Pendleton is the major West Coast base of the United States Marine Corps. It is located on the Southern California coast, in San Diego County, and bordered by Oceanside to the south, San Clemente, Cleveland National Forest, Orange and Riverside counties to the north, and Fallbrook to the east.The base is split into North and South and was established in 1942 to train U.S. Marines for service in World War II.