Construction of Fort St. Frederic was complete by 1734. It included a four-story high tower, commander's quarters, canon, a powder magazine, bakery and other buildings surrounded by an outer stone parapet wall that was nearly square and had six corner bastions covering about an acre. It was the base of three major French operations until July 1, 1759, when the British forced its 200-man garrison to blow up the tower and retreat.
The British did not build a new fort on top of the French ruins. Instead they took three years to construct a new fort, Fort Crown Point, adjacent. A stone and timber fortress, the new fort was a half mile in circumference and shaped like a pentagon. The parade ground covered six acres and contained three stone, two-story barracks, a guard house and an armory. The 40-foot high outer wall was 22-feet thick of timber and limestone, making it Britain's greatest military installation in North America.
Fort Crown Point was the launching point for British forces that brought about the surrender of Montreal in 1760. The fort was destroyed April 23, 1775, when a fire ignited the powder magazine and its 100 barrels of powder causing a huge explosion.
Americans captured the remains of the fort May 11, 1775, and its 111 canon. They transported 29 of the canon overland to Boston to lift the British siege.