British General Francis McLean began Fort George at Castine in June 1779. Massachusetts sent the Penobscot Expedition to capture it, but divided command, delay, and the arrival of a British relief fleet produced a disastrous American defeat. Britain retained the fort until peace, making it the last British post surrendered at the war's conclusion.

The action occurred within a campaign in which commanders relied on speed, imperfect intelligence, and local knowledge. Eighteenth-century fighting was often decided by terrain, roads, fields of fire, unit cohesion, and the ability to communicate under pressure. Militia and Continental soldiers fought beside men whose experience and training varied widely, while Loyalist and British forces faced similar problems of coordination. Casualties carried the war back into surrounding households and communities. The site is consequently important not only for the immediate clash but also for what it reveals about the Revolution as a violent civil and military struggle.

The surviving marker text adds further detail: This Fortress, 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 WAR for INDEPENDENCE. They again occupied the fort on September 1, 1814, rebuilt and mounted it with 60 cannon and evacuated a second time April 27, 1815. Immediately taken possession of the the UNITED STATES, it again rebuilt strengthened and garrisoned until March 1819, it was permanendy (sic) abandoned as a military post. On June 18, 1780, General Peleg Wadworth and Major Benjamin Barton, held as prisoners of war and confined in the barracks, escaped by scaling the North wall during the night, thence following the course of Wadsworth Road to the cove and safety

The marker at Fort George Marker makes this history legible in a modern landscape that has changed substantially since the eighteenth century. Its value lies in identifying the approximate place and connecting it to documented people, movements, and institutions. Visitors should distinguish the historic event from the later act of commemoration: the marker is evidence of how the episode has been remembered, while its text and setting guide interpretation of the original event. Considered with contemporary records and the broader campaign, the location adds geographic meaning to a story that might otherwise survive only as names and dates.