This accurate pictorial history will acquaint the reader with the seacoast defenses of Boston Harbor. Fortified since the the 1600s, seacoast defenses provided important protection for the new seaport. By the Civil War, strong granite fortresses guarded the seaward approaches to the Port of Boston. Later, powerful long-range guns and mortars protected the seaport. During World War II, the most sophisticated and powerful guns existing were installed. These guns used the first computers and radar systems developed for the military for target acquisition and tracking. In The Military History of Boston's Harbor Islands, great care has been taken to identify harbor defense systems at all of the harbor islands, mainland forts, and the observation and radar towers from Nahant to Scituate. The book identifies and explains the long-abandoned granite and concrete monoliths of Boston Harbor. The Military History of Boston's Harbor Islands briefly describes Edgar Allan Poe's tour of duty in Boston Harbor, the impact that Col. Sylvanus Thayer had on Boston's seacoast fortifications, and many mysterious structures at the harbor forts.