Before the Army arrived in any formal way, Campo was a stagecoach stop. In 1869, John Capron established a regular run from San Diego through Dulzura and Campo to Yuma, and the route operated for over four decades. The Larkin family ran the telegraph line and the stagecoach stop, and commerce followed. Commerce, as often happens on frontier routes, also attracted crime.

The December 1875 gunfight at Gaskill Brothers' Stone Store sent the Army's attention to this corner of San Diego County for the first time. Company G of the 1st Cavalry Regiment was dispatched from San Diego. Lieutenant Storey commanded a detachment of ten troopers — and after shooting himself in the hip, detailed four of them to 'outpost' duty near Campo. This was the first regular military presence in what would eventually become Camp Lockett.

Small cavalry detachments returned periodically throughout the late nineteenth century, responding to outlaw assemblies near Tecate in 1876, to cross-border incidents involving Yaqui who had mutinied from the Mexican Army in 1895, and to border security concerns triggered by the Zimmermann Telegram in 1917.

The modern camp took shape in 1941, as the United States built military infrastructure along its southern border in anticipation of war. Camp Lockett was the last base constructed for California. Using standard Army Quartermaster Corps plans, the installation went up with barracks, officers quarters, stables, a veterinary facility, a motor pool, a hospital, a chapel, and a post exchange — the full infrastructure of a cavalry post, because the soldiers stationed here still used horses.

The 10th and 28th Cavalry Regiments were among the units stationed at Camp Lockett during the war years. These were Buffalo Soldier regiments — African American cavalry with histories stretching back to the post-Civil War frontier army. They were assigned to guard the US-Mexico border and defend southern California and Arizona. The Western Defense Command's Southern Land Frontier Sector also moved to the camp, responsible for planning the defense of the entire southern tier.

And yet the soldiers could not eat in certain nearby restaurants. As was common at the time, Camp Lockett was racially segregated, and Black soldiers from the base were refused service in Jacumba — a small town a few miles east where the border terrain was particularly difficult to monitor. Men assigned to defend the country against foreign threat could not order a meal in a town within that country. The Campo border crossing was closed during this period of military buildup.

The convalescent hospital at Camp Lockett remained active until June 1946, when the facility closed and was declared surplus. By 1949 the Army had begun disposing of the property. Leased land reverted to original owners. Six hundred acres were transferred to San Diego County. Thirty-nine acres went to the Mountain Empire Union High School District. Part of the remaining land was repurposed as a juvenile detention facility — Rancho del Campo and Rancho del Rayo — operated by the San Diego County Probation Department.

In 2003 the former base was designated a Historic District by the State of California, and in 2009 it received designation as a California Historical Landmark. By 2009, the Probation Department announced plans to shut down its facilities on the site. The 52 surviving buildings from the period of significance — wood-framed mobilization architecture, stables, a firehouse, the old Gaskill Stone Store itself — constitute a cultural landscape that spans nearly a century of border military history.

An Italian Prisoners of War shrine sits about a mile north of the main encampment, mortared into a bedrock outcrop with a glass-enclosed Catholic statuette and engraved stone — a reminder that Camp Lockett held captives as well as soldiers. Eleven original circulation routes from the 1941 construction period remain. The oak grove in Chaffee Park still stands.

Campo is a small place at the end of a long highway. The military built and abandoned it. The Buffalo Soldiers served and returned home to a country still segregated. The juvenile detention facility ran its course. What remains is a cluster of old buildings on the borderland, designated and planned for and slowly becoming a county park — a place where the strata of history are unusually visible to anyone who goes looking.