Fort Warren - View this location on map This massive pentagonal fortification--its outer walls of Quincy granite are eight feet thick--was begun in 1834 to protect Boston Harbor. One of the nation's finest 19th century coastal fortifications and the chief work of military engineer Sylvanus Thayer, it is strategically located on Georges Island, midway between the northern and southern arms of the harbor. Fort Warren is the most important Civil War site in New England, as it served as a prison for Confederate leaders and officers, including vice president Alexander Stephens. Battery Jack Adams, an unusual single gun battery within the Fort, was considered to be a key part of Boston Harbor's defense system during the Spanish-American War. Georges Island, Boston, Massachusetts Historical

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