British troops leave Boston Posted on March 23, 2019 by Steve Dunwell Evacuation Day in Boston marks the departure of the British on March 17, 1776, ending the 11-month “Siege of Boston.” Washington had surprised the British with new fortifications and cannons on Dorchester Heights. The “Evacuation” took troops and Tory citizens to Halifax, NS. Evacuation Day a local holiday In Boston, often combined with St. Patrick’s Day. This broadside by Paul Revere shows the troops arriving by ship in 1775.