El Camino Real is widely believed to begin at San Diego and end at Sonoma. Its actual origin is Vera Cruz, on the Atlantic coast of what is now Mexico; crosses southern Mexico, through Mexico city, reaching the Pacific coast at San Blas; resumes across the Sea of Cortés at the Baja California mission at Loreto; and follows the Pacific Trail to San Diego before assuming its Alta California trail. It was a thin line 2300 miles long only as far as Monterey. It was extended to San Francisco, then Sonoma, only after Monterey was settled.

Before El Camino Real was extended northward into Alta California, there were already thirteen Jesuit missions in Baja California Sur, the first, Nuestra Señora de Loreto Concho, established in 1697. Twenty-three were originally established, but ten were abandoned.  After Galvéz expelled the Jesuits in 1768, Dominicans came in and established another eight missions in Baja California Norte, while the Franciscans went to Alta California with Portolá. Only eight of the original Baja California missions are still standing today.