This Fire Control Structure was one of the first two built at Fort Andrews (1). It originally housed the primary base end stations for Batteries McCook, Pope (Fort Revere), and Cushing-Whitman (the combined 12-inch mortar batteries at Fort Andrews). In addition, this building housed the primary BES for the Third Fire Command, which was itself made up of Battery Cushing and Battery Whitman.
The structure was a cemesto building of one story, with an observation gallery above it, that was constructed in a pit some 15 feet deep, such that only the observation windows of the gallery (and a little of the roof) were visible above ground level. Still, its observation instruments would have had an elevation over 120 ft. or more, making this the highest vantage point in the central harbor defenses (the harbor islands). The FCS would have had an unobstructed view across the harbor northerly towards Fort Revere, Fort Dawes, and Fort Warren (2).
Behind this building about 100 ft. to the SW were a fire control switchboard room and a dormitory for the troops who manned the fire control positions. The fort's radio station was located about 300 ft. SE of the FCS.
The plotting rooms for Batteries Whitman and Cushing were located in the casemates of these batteries, along the road that runs SE-NW in front of the mortar pits. The plotting room that served Batteries Rice and McCook was part of the Fort Commander's station in the 1904 Andrews East FCS.
Today (2011), the structure is a tangle of crushed walls, having been collapsed over the years from a series of large trees falling into the pit. However, this is still the only example of a cemesto FCS (once the most common type) remaining in the harbor defenses of Boston.