Old Customhouse, Monterey

The Old Customhouse, located in Monterey County, California, is an adobe building constructed in the Spanish Colonial style around 1827 during the period when Mexico governed the region. It holds the distinction of being California's inaugural California Historical Landmark. This designation commemorates the site where U.S. Commodore John Drake Sloat raised the American flag in 1846, officially incorporating California into the United States.

Following Mexico's victory over Spain and its subsequent independence in 1821, Monterey remained within the Mexican Territory of Alta California for nearly 25 years. To manage the collection of customs duties (taxes) at the port of Monterey Bay, the Mexican government erected the Customhouse, making it the oldest surviving government building in California today.

The Monterey Customhouse garnered significant attention from the Native Sons of the Golden West, who were determined to preserve it from fading into obscurity. Although the property was owned by the United States Government, the Native Sons secured a lease for the buildings and grounds. They embarked on a restoration effort in the early 1900s. Subsequently, the lease was transferred to a State Commission, established by legislative action in 1901, which also allocated funds for further restoration work on the structure.

On June 1, 1932, the Customhouse was officially designated as the first California Historical Landmark. Later, in 1960, it received the status of a National Historic Landmark. It is now an integral part of the larger Monterey State Historic Park, which itself holds National Historic Landmark District status, along with the nearby Larkin House.