This fort, originally known by its garrison as "Fort Penobscot" and named by Admiral Sir George Collier in his reports "Fort Castine" received its present designation from its builder, British general Francis McLean upon its completion in December 1779. It was begun in June and was unsuccessfully besieged from July 29 to August 13 by the combined American land and naval forces on the Penobscot Expedition and was the last post surrendered by the British at the close of the Revolutionary War. As they departed in 1784, the British burned the buildings within the fort.The Penobscot Expedition
British forces again occupied it in September 1814, rebuilt, it and mounted it with sixty cannon. When these troops destroyed and evacuated it in April 1815, American troops rebuilt it again, strengthened it and occupied it until March 1819 when it was permanently abandoned as a military post.
The most important military action relating to Fort George was the Penobscot Expedition of 1779, the largest American naval expedition of the Revolutionary War. Learning that the British were establishing the fort, American authorities in Boston dispatched a naval squadron of nineteen warships under Commodore Dudley Saltonstall and twenty-four transports carrying a force of 1,200 men under General Solomon Lovell to destroy the fort and its garrison. When the Americans reached Penobscot Bay on July 25, however, three British Royal Navy sloops sat in the bay nearby.
After landing his troops ashore, General Lovell decided that trying to take the fort by land was too risky since the British ships could bombard them as they attacked. For days, he asked Commodore Saltonstall to attack the British ships and, even though the American fleet has more ships and more guns, Saltonstall refused.
On August 13, a British naval force consisting of six warships, including a 64-gun ship of the line and four frigates, arrived to relieve the British garrison. Though he still had the British outgunned, Saltonstall ordered his American ships to flee up the Penobscot River and burned them at his order. This forced soldiers who had been part of the assault to find their way back to Boston on foot trough the wilderness.
For his actions, Saltonstall was removed from the service, Paul Revere, who was in charge of artillery for the expedition, was acquitted in a court-martial though is reputation was permanently damaged.
The Penobscot Expedition remained the worst defeat in U.S. Navy history until the attack on Pearl Harbor in 1941.