- In March 1776, the Continental Army under General George Washington began to fortify Dorchester Heights, which overlooked the city of Boston.
- The British were taken by surprise, as they had not expected the Americans to be able to move their artillery up the hill.
- The British commander, General William Howe, realized that he could not defend Boston if the Americans were able to establish a strong position on Dorchester Heights.
- He therefore decided to evacuate the city, and on March 17, 1776, the British fleet sailed out of Boston Harbor.
- The evacuation of Boston was a major victory for the Americans, and it boosted their morale.
- It also showed that the Americans were capable of defeating the British, and it helped to convince France to enter the war on the side of the Americans.