Thomas O. Larkin

Thomas Oliver Larkin (September 16, 1802 – October 27, 1858), known later in life as Don Tomás Larkin, was an American diplomat and businessman.

After some success and several business failures on the east coast, his elder half-brother, Alta California pioneer businessman John B. R. Cooper, invited him to join him in on the west coast, propelling him to success and wealth.

Larkin served as the only U.S. consul to Alta California during the Mexican era and was covertly involved in U.S. plans to annex California from Mexico. Following the American Conquest of California and the end of the Mexican-American War, Larkin was a delegate to the Monterey Constitutional Convention in 1849 and a signatory of the Constitution of California.