Fort O'Brien

 (1775-1781, 1808-1818, 1863-1865) - A Patriot Revolutionary War fort established in 1775 by Captain Jeremiah O'Brien and Colonel Benjamin Foster in Washington County, Maine. Initially named Fort Machias and later renamed Fort O'Brien after Captain Jeremiah O'Brien one of the founders. Paired with Fort Foster (3) on the other side of the Machias River. Reestablished as a Second System fort in 1808 and as a U.S. Civil War fort in 1863. Finally abandoned in 1865.

Revolutionary War (1775-1783)
Initially built as a small breastworks on the west bank of the Machias River in anticipation of a retaliatory British raid for the Patriot capture of a British ship, the Margaretta. The defenders were eventually driven off by a squadron of four British ships under Sir George Collier on 14 Aug 1777. The British departed soon after and the fort was reoccupied by the Patriot forces.

The fort was improved after the raid and the garrison was increased to 300 troops but the fort was not attacked again during the Revolutionary War.

Second System (1808-1816)
Rebuilt in 1808 as a Second System fortification that included a blockhouse and a circular stone battery mounting four heavy guns.

War of 1812 (1812-1814)
During the War of 1812 in September of 1814 some 900 British troops on five men-of-war seized the fort, burned it down and carried off the armament.

U.S. Civil War (1861-1865)
During the U.S. Civil War Fort O'Brien was rebuilt as a new 150' long earthworks battery and armed with three 32-pounder smooth bore cannons and two 24-pounder rifled cannons.

Current Status
Part of Fort O'Brien State Historic Site, Washington County, Maine. Two fort sites, a magazine site and stone building foundations can be seen. The cannon that was emplaced in the Fort O'Brien earthworks was not in place during our visit.

Sources:
 * , page 369

Links:
 * North American Forts - Fort O'Brien
 * Wikipedia - Fort O'Brien
 * Maine Parks - Fort O'Brien State Historic Site