During the winter of 1775–76, an attempt by the Patriots to capture Quebec failed, and the buildup of British forces at Halifax, Nova Scotia, precluded that colony from joining the 13 colonies. The Americans were able to capture a British fort at Ticonderoga, New York, and to drag its cannon over the snow to the outskirts of Boston. The appearance of troops and a cannon on Dorchester Heights outside Boston led the British Army to evacuate the city on March 17, 1776.