Marine Corps Base Camp Pendleton is the major West Coast base of the United States Marine Corps and serves as its prime amphibious training base. It is located on the Southern California coast, bordered by Oceanside to the south, San Clemente to the north, and Fallbrook to the east.

The base was established in 1942 to train U.S. Marines for service in World War II. By October 1944, Camp Pendleton was declared a "permanent installation" and by 1946, it became the home of the 1st Marine Division. It is named after Marine General Joseph Henry Pendleton, who long advocated setting up a West Coast training base for the Marine Corps. Today it is the home to myriad Operating Force units including the I Marine Expeditionary Force and various training commands.

In 1769, a Spaniard by the name of Capt. Gaspar de Portola led an expeditionary force northward from lower California, seeking to establish Franciscan missions throughout California. On July 20 of that same year, the expedition arrived at the location now known as Camp Pendleton, and as it was the holy day St. Margaret, they baptized the land in the name of Santa Margarita.