33 C.F.R. § 80.130
Boston Harbor entrance
A line drawn from the easternmost tower at Nahant, charted in approximate position latitude 42°25.4′ N., longitude 70°54.6′ W., to Boston Lighted Horn Buoy “B”; thence to the esternmost radio tower at Hull, charted in approximate position latitude 42°16.7′ N., longitude 70°52.6′ W.