Description: This five-story concrete tower with attached barracks was built on a leased site under the authority of the Boston Harbor Defense Command, and was jointly used as a Base-End Station for Fort Dearborn and for Fort Ruckman in Nahant, Mass. It is currently the Park HQ and Visitor Center for Halibut Point State Park. The roof deck was used for Boston's anti-aircraft intelligence service (AAIS OP 18-Boston). The fifth-story level was used for Fort Ruckman (B9 S9 for Battery 104/Murphy). The fourth-story level was used for the Boston Harbor Command - Second Gun Group (C4/2), and the third-story level was used for Fort Dearborn (B1 S1 for Battery 103/Seaman).