United States Custom House (San Francisco, Calif.)

In 1846 American troops signalled the occupation of San Francisco by raising an American flag above the former Mexican customhouse. The port, then known as Yuerba Beuna, fell into American control. The military retained jurisdiction over tariff collection and other civic affairs until California's interim government was established in 1849. The administration of dues and the regulation of maritime traffic for the port was eventually transferred to the United States Customs Service, a federal agency established in 1789 as a subordinate body of the Treasury Department.

Through the middle of the 19th century, San Francisco was California's principal commercial port. Customs officials were charged with the regulation of international maritime commerce and were responsible for administering United States customs laws. Responsibilities included collecting duties on imported goods, enforcing export control laws, registering and licensing vessels, and documenting the entry and clearance of merchandise, sailors and passengers.

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