17 March 1776: British Evacuate Boston
On March 17, 1776, British forces evacuated Boston after an eleven-month siege, marking the first major American victory in the Revolutionary War.
The siege had begun in April 1775, following the Battles of Lexington and Concord. The Continental Army, initially a disorganized collection of militia, surrounded Boston while the British controlled the city and harbor. For months, a stalemate persisted—the Americans lacked the artillery to force the British out, while the British couldn’t break through American lines.
Everything changed when Henry Knox, a young Boston bookseller turned artillery officer, accomplished the seemingly impossible. In the dead of winter, Knox led an expedition to Fort Ticonderoga and transported sixty tons of captured cannons across 300 miles of frozen wilderness to the outskirts of Boston.
Under cover of darkness on March 4th, General George Washington’s forces fortified Dorchester Heights, positioning Knox’s cannons to command both the city and harbor. British General William Howe awoke to find his entire position untenable. A planned counterattack was thwarted by a violent storm, and Howe had no choice but to negotiate a withdrawal.
On March 17th, approximately 9,000 British soldiers and 1,100 Loyalist civilians sailed out of Boston Harbor, never to return. Washington’s troops marched triumphantly into the city, ending British occupation of Massachusetts.
The evacuation proved that the Continental Army could stand against the world’s most powerful military. For Boston, March 17th became “Evacuation Day,” a local holiday still celebrated today—conveniently coinciding with St. Patrick’s Day.
