Since the fighting at Lexington and Concord in April 1775, the Continental Army had kept the British bottled up in Boston. The deadlock broke when Henry Knox hauled heavy artillery from Fort Ticonderoga across the frozen countryside and Washington's men fortified Dorchester Heights, the high ground overlooking the city and harbor, in a single night in early March. With his ships and garrison under the American guns, Howe chose to leave. On March 17, 1776, nearly 10,000 British troops and loyalists sailed away, giving Washington his first major victory of the war.
Taking Dorchester Heights was a feat of preparation and nerve. On the night of March 4, thousands of Continental soldiers worked in near silence, dragging up pre-built timber frames, bundles of brushwood and bales of hay to form breastworks, because the frozen ground was too hard to dig. When Howe looked up the next morning, he saw a fortress that had not been there at dusk. A storm wrecked his plans for a counterattack, and evacuation was the only option left.
The British left for Halifax, Nova Scotia, taking with them many loyalist families who could no longer stay in a city that had turned against the Crown. Boston, which had been at the centre of colonial resistance since the Stamp Act protests and the Boston Massacre, was never occupied again. Abigail Adams greeted the news with a line from scripture: "Surely it is the Lord's doings and it is marvelous in our eyes." Every March 17, Suffolk County still marks Evacuation Day as a public holiday, so the day Boston celebrates its liberation is also St. Patrick's Day.
Key people: George Washington, William Howe, Henry Knox