This handsome brick building was completed in 1852 for use as a City Hall. It served as the State Capitol Building during 1853 and 1854, when Benicia was the capitol of the State of California for a period of 13 months. The Senate Chambers were on the first floor, and the Assembly met on the second floor. In addition, there were several committee rooms. In 1854, the building also housed the State Treasury since no wooden structure was considered safe for this purpose.

Historians record that there were good wooden sidewalks from the Capitol building to the town so the building could be reached dry-shod in all seasons.