Fort Delaware State Park is a Delaware state park on Pea Patch Island in New Castle County, Delaware, in the United States. A fortress was built on Pea Patch Island by the United States Army in 1815, near the conclusion of the War of 1812, to protect the harbors of Wilmington, Delaware and Philadelphia, Pennsylvania. The fort was burned and rebuilt in the years prior to the American Civil War, and soon after the start of the war the fort was converted to a Prisoner of War camp. Fort Delaware continued to protect the mouth of the Delaware River through World War I and II. Pea Patch Island and Fort Delaware was declared surplus land by the United States Department of Defense in 1945.