[6] The first fort to be constructed on Castle Island resulted from a visit by Governor John Winthrop; it was partly financed by him and the council.

Roger Ludlow and Captain John Mason of Dorchester, producing a "castle with mud walls" with masonry of oyster shell lime in which cannon were mounted to defend Boston from attack by sea.

It was designed by Wolfgang William Romer, the chief engineer of British forces in the American colonies,[9] and its armament was nearly doubled to 100 guns.

[4] In the years leading up to the American Revolution, Castle William became a refuge for British officials during periods of unrest and rioting in Boston.

[10] Violence forced provincial leaders and British soldiers to take shelter within the fort in the wake of events such as the Stamp Act crisis in 1765 and the Boston Massacre in 1770.

It was not until the Continental Army led by George Washington managed the fortification of Dorchester Heights that Castle William was threatened and the British evacuated Boston in March 1776.

[14][15][16] The Secretary of War's report on fortifications for December 1811 describes the fort as "...a regular pentagon, with bastions of masonry, mounting 42 heavy cannon, with two [additional] batteries for six guns...".

[17] During the War of 1812, a squadron of the British Navy repeatedly captured American merchant and fishing vessels in Massachusetts Bay; however, they never attempted an attack on the port of Boston due to the strength of Fort Independence.

[18] Work on the present fort began in 1833 under the third system of US fortifications, supervised by Colonel Sylvanus Thayer, one of the nation's leading military engineers of the time.

At the height of its strength during the American Civil War, it mounted 96 cannon, some of which were 15-inch Rodman guns capable of firing a 450-pound shot more than 3 miles (4.8 km).

[20][21] A small part of Castle William's brick structure remains in the rear portion of the present fort, but is covered up by subsequent stonework.

Olmsted had originally envisioned a parkway to be known as the Dorchesterway that would connect Castle Island (via a new earthen causeway) to the rest of the Emerald Necklace.

[23] The Federal government briefly reclaimed Castle Island in 1898 during the Spanish American War, but it was quickly returned to the city of Boston in 1899.

Edgar Allan Poe was serving with the 1st United States Artillery Regiment at Fort Independence in 1827, and he purportedly was inspired by the story to write "The Cask of Amontillado".

After World War II, Lieutenant Massie's remains were moved to the Fort Devens Cemetery near the town of Ayer, Massachusetts.