CASTLE WILLIAM. Castle William, named for King William III, was the fortification on Castle Island that was the principal inner defense of Boston Harbor. Garrisoned by a small company of provincial soldiers before the arrival of British troops in September 1768, it was demolished when the British evacuated Boston in March 1776. The site is no longer an island, having been connected to the town of Dorchester with landfill in the nineteenth century.
revised by Harold E. Selesky