When the American Revolutionary War broke out in April 1775, the Machias area became one of interest to British authorities in besieged Boston as a source of lumber and supplies.

An expedition to the area to acquire materials resulted in the naval Battle of Machias on June 11–12, 1775, in which a small Royal Navy ship was captured by the colonists led by Jeremiah O'Brien, for whom the fort is named.

After this event a number of fortifications were erected on the Machias River, including a four-gun battery at this point.

[2] In the War of 1812, American forces garrisoned the fort, which often held British POWs brought in by privateers.

Although its military equipment was removed, a Civil War-era 12-pound "Napoleon" cannon now stands on site.