Mount Defiance, an eight hundred forty-foot hill in Ticonderoga on the New York side of Lake Champlain, overlooks both Fort Ticonderoga and Mount Independence and became a decisive feature in the region’s military geography. Formerly called Sugar Loaf, it was recognized as commanding ground during the era when the forts guarded this strategic corridor, yet it was left unfortified because it was thought inaccessible. In 1777, that miscalculation proved disastrous when British forces placed artillery on its summit during the siege of Fort Ticonderoga. Their elevated guns made the American positions untenable and forced the Continental Army to abandon both forts without battle.