Forts of Boston Harbor

Throughout its history, Boston Harbor served as a strategically important military port in wartime. First the British and later the United States government built military outposts and forts across the Boston Harbor Islands to prevent an attack from the sea. During the 1800s and 1900s, the US military continued to update forts in alignment with new advancements in defense systems and technologies. From behind imposing walls, the heavy guns of the island forts overlooked the harbor and protected it for over a century. Though their defenses were never tested in battle and some no longer remain visible today, these forts nonetheless played an important role in the history of Boston and of the United States.

Learn more about these historic structures using the interactive map below.