In 1969, the site was registered as California Historical Landmark #830. Then on September 3, 1971, it was added to the National Register of Historic as Old Town San Diego Historic District.
The first European settlement on the West Coast of the present-day United States was the San Diego Presidio, a military outpost of Spanish California, founded by Gaspar Portola in 1769. Mission San Diego de Alcala was founded by Father Junipero Serra the same year. The Presidio and Mission were originally built on a bluff, Presidio Hill, which is now the site of the city-owned Presidio Park and which is immediately adjacent to Old Town State Historic Park. After 5 years the Mission moved to a location several miles upriver at the present site of Mission San Diego de Alcalá. Presidio Hill remained the primary settlement for several decades because it was defensible against attack by European enemies or hostile Indians. As the need for defense decreased, settlers preferred to live at the base of the hill because of greater convenience. In the 1820s the town of San Diego grew up at the base of the bluff, at the site commemorated by Old Town San Diego State Historic Park. The Presidio was abandoned and fell into disrepair.
During the pueblo period following Mexican independence, the Old Town area was the commercial and governmental hub of the region, even though its population was never more than a few hundred. San Diego during this period is vividly described by Richard Henry Dana , Jr. in his classic book Two Years Before the Mast. In 1834 the Mexican government granted San Diego the status of a pueblo or chartered town; however, its pueblo status was revoked in 1838 due to declining population. One problem limiting the town’s growth was its location far from navigable water. All imports and exports had to be brought ashore in Point Loma and carried several miles over the La Playa Trail to the town.
When California was admitted to the United States in 1850, San Diego (still largely limited to the Old Town area) was made the county seat of San Diego County, even though the town’s population was only 650. The Old Town area remained the heart of the city of San Diego until the 1860s, when a newcomer to San Diego named Alonzo Horton began to promote development at the site of present-day Downtown San Diego. Residents and businesses quickly abandoned “Old Town” for Horton’s “New Town” because of New Town’s proximity to shipping. In 1871 government records were moved from Old Town to a new county courthouse in New Town, and Downtown permanently eclipsed Old Town as the focal point of San Diego.
Old Town San Diego State Historic Park preserves and recreates Old Town as it existed during the Mexican and early American periods, from its settlement in 1821, through 1872 when it lost its dominant position to Downtown.