The Power House is a power house on the northwest coast of Alcatraz Island, off the coast of San Francisco, USA. It was constructed in 1939 for $186,000 as part of a $1.1 million modernization scheme which also included the water tower, New Industries Building, officers quarters and remodeling of the D-block. The white powerhouse smokestack and lighthouse were said to give an "appearance of a ship's mast on either side of the island". "A Warning. Keep Off. Only Government permitted within 200 yards" sign lay in front of the powerhouse to deter people landing on the island at the point.