4. Castle Williams on Governors Island

Located on the west point of Governors Island, Castle Williams is a circular defensive structure, named after its designer, Lieutenant Colonel Jonathan Williams. Castle Williams’ cannons were never used to fire against an enemy; they were used instead for ceremonial purposes.

Built on a rocky outcropping facing New York harbor in 1811, Castle Williams was served as a center of fortification during the War of 1812. Along with Fort Jay and South Battery on the island, it made up the inner harbor of a larger defense system called the Second American System of coastal defense, which protected American shipping from British interference.

Castle Williams was individually listed on the National Register of Historic Places on July 31, 1972. The castle is also located along the boundaries of Governors Island National Monument, created by Presidential Proclamations signed in 2001 and 2003.