On March 17, 1776, British forces are forced to evacuate Boston following General George Washington’s successful placement of fortifications and cannons on Dorchester Heights, which overlooks the city from the south.

During the evening of March 4, Major General John Thomas, under orders from Washington, secretly led a force of 800 soldiers and 1,200 workers to Dorchester Heights and began fortifying the area. To cover the sound of the construction, American cannons, besieging Boston from another location, began a noisy bombardment of the outskirts of the city. By the morning, more than a dozen cannons from Fort Ticonderoga had been brought within the Dorchester Heights fortifications. British General Sir William Howe hoped to use the British ships in Boston Harbor to destroy the American position, but a storm set in, giving the Americans ample time to complete the fortifications and set up their artillery. Realizing their position was now indefensible, 11,000 British troops and some 1,000 Loyalists departed Boston by ship on March 17, sailing to the safety of Halifax, Nova Scotia.

The bloodless liberation of Boston by the Patriots brought an end to a hated eight-year British occupation of the city, known for such infamous events as the “Boston Massacre,” in which five colonists were shot and killed by British soldiers. The British fleet had first entered Boston Harbor on October 2, 1768, carrying 1,000 soldiers. Having soldiers living among them in tents on Boston Common–a standing army in 18th-century parlance–infuriated Bostonians.

For the victory, General Washington, commander of the Continental Army, was presented with the first medal ever awarded by the Continental Congress.