U.S. Customhouse
Also known as: Old Customhouse
Why it's listed
Built in 1827 by the Mexican Government as a small two-room adobe, the Old Custom House in Monterey grew into a long, one-story, tile-roofed building of adobe and rock with two-story hip-roofed wings at each end. Thomas O. Larkin, an American merchant and master-builder, added the second story of the north wing, the central section and the south wing between 1841 and 1846. Verandas were added on the ocean side. The building measures 135 by 34 feet. It served as the only custom house north of Mexico until 1845, collecting duties on the California hide and tallow trade that largely funded Mexican government operations. On July 7, 1846, Commodore John D. Sloat raised the American flag here and proclaimed California part of the United States. After use as a U.S. custom house, a residence and a lodge hall, it was restored and became a state museum in 1930. It is an example of Monterey Colonial public architecture.
Significance in brief: The nomination calls it an excellent example of the Monterey Colonial style applied to a public building, and the oldest public building still standing on the West Coast. It was the only custom house in Mexican California until 1845, and Commodore John D. Sloat raised the American flag here on July 7, 1846.
Machine-generated summary. This summary was generated by a language model from the official nomination document and has not been reviewed line by line by an editor. It may contain errors. Check the source document before relying on any detail. Source: nomination document (PDF) · National Archives catalog entry. NRHP reference 66000217, listed October 15, 1966. Summary generated October 2026 (model claude-sonnet-5-5, prompt v1.0-2026-10-29, confidence medium).
Key facts
| Address | Calle Principal at Decatur St., Monterey |
|---|---|
| County | Monterey County |
| Listed | October 15, 1966 |
| Reference number | 66000217 |
| Resource type | Building |
| Period of significance | 1827, 1841-42 (specific dates) |
| Architect / builder | Thomas O. Larkin (1841-46 enlargement, under contract with the Mexican Government); original 1827 section erected by the Mexican Government |
| Architectural style | Monterey Colonial |
| Areas of significance | Architecture |
| Level of significance | National |
| National Historic Landmark | Yes, designated December 19, 1960 |
| Status (as stated in the nomination) | Restored, maintained in excellent condition, and open to visitors as a museum and State Historical Monument. |
| Acreage | 2 |
| Within district | Monterey Old Town Historic District |
| Coordinates | 36.60322, -121.89343 (NPS GIS) |
What listing means for this property
National Register listing is honorary: it recognises significance and does not restrict what a private owner may do without federal money or permits. It unlocks the 20% federal rehabilitation tax credit for income-producing buildings, state credits in many states, and Section 106 review when federal agencies are involved. See what listing means in practice.
General information, not legal or tax advice. Rules change; confirm with your State Historic Preservation Office or a qualified adviser.
Sources and further reading
- National Park Service, National Register of Historic Places database (snapshot May 2026), reference 66000217.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q7083808
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.