The Powerhouse building was designed by San Francisco architect Charles Peter Weeks (1870-1928), who had studied at the Ecole de Beaux Arts in Paris and who had worked on several buildings on the UC Berkeley campus. Built in 1912, it's a tall, one-story rectangular building with hipped ceramic roof. The 20th Street (front) and backside facing north have five tall arched bays, and the gables at the west and east end have similar windows.

The powerhouse served several electrical distribution functions as well as being the site of powerful compressors that provided pneumatic pressure for use throughout the shipyards. These compressors can still be seen inside the building.

The powerhouse building was built soon after Bethlehem Steel bought the Union Iron Works in 1905 (Union Ironworks retained its name until 1917). It is indicative of the ambitions Bethlehem had for its new west coast shipyard that the building was given such prominence and careful design treatment.