Bienvenidos to the Ranch House, former home of the Commanding General of Marine Corps Base Camp Pendleton. Your tour of the Ranch House Complex features more than half a century of traditional hospitality and generosity. Rancho Santa Margarita history includes key events and figures from the history of California and the nation. The Ranch House has provided shelter and an administrative center for inhabitants of the Rancho Santa Margarita since 1841. The wide adobe walls of the rancho, the rustle of eucalyptus leaves and the vivid purples of bougainvillea evoke mental images of early Native Americans, Spanish explorers, turbulent Mexican and American conquest, giant cattle drives, exciting rodeos, and fiestas enlivened by laughter and Spanish guitars.

The Rancho derives its name from the feast day of St. Margaret of Antioch. It was recorded by Father Crespi on July 20, 1769, as he traveled northward through this valley as part of Gaspar de Portolà expedition. Later, the valley was included as part of Mission San Luis Rey. Records from 1827 describe a building, generally in the Ranch House area, used for storage and shelter. Since then, the Rancho has seen several owners and many changes. Pío and Andrés Pico applied to the Mexican Governor for the Rancho Santa Margarita land and thereby became the owners of the largest Mexican land grant in Southern California. A young Englishman, John Forster, married Pío and Andrés' sister, Ysidora and gained two large properties of his own. Don Juan (John) Forster later paid off Pío's large gambling debt and added to his holding the Rancho Santa Margarita y Las Flores, creating a land holding totaling more than 335 square miles extending from the Ranch House north nearly to El Toro. His children sold the Rancho to James Flood, who expressed an enthusiasm and interest in it. Flood later split the property with his friend and ranch manager, Richard O'Neill.

Sometime later, half the interest of the Ranch was deeded to O'Neill. Following the deaths of both James Flood and Richard O'Neill, the Rancho was managed by Richard's son Jerome. He enclosed the buggy shed and expanded the house to its current size. After Jerome's death in 1926, the Rancho was operated by various managers on behalf of the Flood and O'NeilI heirs. During this time, General Joseph H. Pendleton a retired Marine had been promoting the idea of a West Coast Marine Corps training facility. In 1942, with the U.S. fighting the Japanese in the Pacific, the U.S. government purchased 125,000 acres of Rancho Santa Margarita y Las Flores under the Second War Powers Act. Unfortunately, General Pendleton died in February before seeing his dream become a reality. On September 25, 1942, General Pendleton's widow Mary Fay along with President Franklin D. Roosevelt dedicated this vast base in his honor.