The logic was simple: 400 square miles of barren desert, barren mountains, and badlands where you could fire from .33 caliber to 90mm without hitting anything you needed to preserve. The Borrego Valley Maneuver Area opened in March 1942, three months after Pearl Harbor, as the US military scrambled to build training infrastructure for a war that was consuming resources and personnel at a scale the country had never experienced. By August 1944, when the facility closed, American soldiers, sailors, and marines had practiced bombing, strafing, rocket attacks, and night-driving on this Colorado Desert terrain. Then the land returned to California, and the desert began its slow work of erasing what had been built.
The Borrego Valley Maneuver Area operated as a subcamp of Camp Callan, a large coastal anti-aircraft training center established at La Jolla in 1941. Camp Callan handled the classroom and initial training; the Borrego Springs facility provided the live-fire and maneuver space that coastal training simply could not offer. The Western Defense Command oversaw operations, recognizing that the desert's vast open spaces and clear skies were ideal for the full range of military training activities that the facility's designers envisioned. Anti-aircraft artillery was installed and used. The California Institute of Technology contributed expertise to the rocket training program. The US Navy flew carrier aircraft from San Diego Naval Air Station to the bombing ranges, practicing high-altitude bombing, dive-bombing, and strafing against targets laid out on the desert floor.
Within the larger Maneuver Area, the US Marines built Camp Ensign in 1943 on the site of the Ensign Ranch, whose date palm orchards were converted into a military training camp for troops from San Diego. The training at Camp Ensign was practical and unglamorous: two weeks of driving military trucks at night. Nighttime vehicle operations were critical skills for an army that needed to move in darkness across unfamiliar terrain without lights that would reveal positions to enemy observers. The date palms that had marked the Ensign Ranch gave way to the sounds of diesel engines navigating desert roads in darkness. The former Base Headquarters is now located near the Borrego Springs Spa and Resort; the Ensign Ranch Airfield that was built to support the camp has no visible remains.
Three miles south of the main Maneuver Area, the Borrego Hotel Target Area offered 222 acres dedicated to naval aviation training. Three concentric circles marked the target for carrier aircraft practicing high-altitude bombing, dive-bombing, and strafing — skills that would be tested in Pacific combat against Japanese shipping and shore installations. The Target Area opened in 1941 and operated until 1955, supported by the Naval Outlying Field at Ocotillo Dry Lake and the Borrego Hotel Naval Outlying Landing Field, which provided emergency landing facilities on dirt runways built on Halfhill Dry Lake. The Benson Bombing Range at nearby Ocotillo Wells provided additional space for training runs. Together, these ranges gave naval aviators hundreds of practice approaches over terrain that offered clear visual reference without civilian hazards.
When the Borrego Valley Maneuver Area closed in August 1944, the land reverted to the State of California, which eventually incorporated it into Anza-Borrego Desert State Park. The desert's capacity to erase human construction is formidable: without maintenance, roads fill with sand, structures deteriorate in the extreme heat and cold, and wind covers what the sun bleaches. No remains of the Ensign Ranch Airfield survive; the Borrego Hotel Naval Outlying Landing Field has no visible traces. The desert that the military chose because it was already damaged — barren terrain where training exercises would cause no significant harm — proved more durable than the infrastructure built on it. Walk those desert miles today and the landscape gives few hints that tens of thousands of American servicemembers trained here for a war that would determine the direction of the twentieth century.
The Borrego Valley Maneuver Area centered at approximately 33.233°N, 116.357°W in the Borrego Valley of San Diego County, within what is now Anza-Borrego Desert State Park. The flat valley floor and surrounding mountain terrain that made it ideal for wartime training are clearly visible from altitude. Borrego Valley Airport (L08) in Borrego Springs provides the nearest airstrip. The bombing target areas were located approximately 3 miles south of the valley center; the Benson Bombing Range at Ocotillo Wells is visible as a distinctive flat playa approximately 15 miles to the southeast. The valley's clear desert air makes low-altitude flying comfortable in most seasons.