The Fortification of Dorchester Heights was a decisive action early in the American Revolutionary War that precipitated the end of the siege of Boston and the withdrawal of British troops from that city.

The idea of bringing the cannons from Ticonderoga to the siege was raised by Colonel Henry Knox. Knox was eventually given the assignment to transport weapons from Ticonderoga to Cambridge. Knox went to Ticonderoga in November 1775, and, over the course of three winter months, moved 60 tons of cannons and other armaments by boat, horse and ox-drawn sledges, and manpower, along poor-quality roads, across two semi-frozen rivers, and through the forests and swamps of the sparsely inhabited Berkshires to the Boston area.

On March 4, 1776, troops from the Continental Army under George Washington's command occupied Dorchester Heights, a series of low hills with a commanding view of Boston and its harbor, and mounted powerful cannons there threatening the city and the Navy ships in the harbor. General William Howe, commander of the British forces occupying Boston, planned an attack to dislodge them. However, after a snowstorm prevented its execution, Howe withdrew instead. British forces, accompanied by Loyalists who had fled to the city during the siege, evacuated the city on March 17 and sailed to Halifax, Nova Scotia.