In 1634 Governor Dudley of Massachusetts Bay Colony selected Castle Island for the sea defense of Boston. The first fortifications were an earthwork and 2 platforms and 3 cannons. A pine log fort (1644), the second fort, was replaced with a more substantial structure in 1653. This burned down and was quickly replaced with the fourth fort (1673), These forts, and the succeeding ones, to this day are know as "The Castle".

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In 1703, Colonel Romer's brick, 4-bastiened fort, begun in 1701, was dedicated. For most of the 1700's thereafter, this fort was generally known as "Castle William", after William III of Orange, King of England. It was armed with 72 cannons, ranging from 9lbs to 42lbs. In 1776, the British, evacuating Boston, destroyed the island's fortifications which were repaired shortly thereafter by troops under Lt. Colonel Paul Revere. In 1778, Colonel Richard Gridley "renewed the works."

 

Massachusetts ceded Castle Island to the United States in 1798. President John Adams came to dedicate  new fort as "Fort Independence" in 1799.

 

This, the island's 7th fort, 5-bastiened and of brick, was built by Colonel John Foncin between 1801 and 1803.  By 1551, Colonel Sylvanus Thayer, "the Father of West Point." completely reconstructed the eighth and present fort on Castle Island: doubling the former height, expanding its perimeter, constructing casemated interiors and replacing brick with granite from the quarries at Rockport, Mass. Colonel Foncin's 5-bastioned concept was retained.