Siege of Boston

The Siege of Boston began immediately after Lexington and Concord and lasted nearly a year. Following the April 19 battles, thousands of Massachusetts militiamen spontaneously converged on Boston, trapping the British garrison inside the city. Within weeks, 16,000 colonial troops ringed the city. In June 1775, colonial forces occupied Breed's Hill and Bunker Hill, prompting the costly British assault that became the Battle of Bunker Hill. In July, George Washington arrived from Virginia to take command, finding a diverse, poorly equipped army he immediately set about transforming.

Washington faced acute shortages throughout the siege. At one point the army had only thirty-six barrels of powder — barely nine shots per man. Despite these difficulties he maintained the siege, prevented any British breakout, and authorized the first American naval operations. Henry Knox led a remarkable expedition to drag 59 captured cannon from Fort Ticonderoga across 300 miles of frozen wilderness to Boston, arriving in January 1776.

On the night of March 4-5, 1776, Washington moved Knox's cannon onto Dorchester Heights overlooking Boston Harbor in a single night, using artillery bombardment to cover the sound of construction. When dawn revealed the fortified heights commanding the harbor, General Howe concluded Boston was no longer defensible. On March 17, 1776 — still celebrated as Evacuation Day in Boston — the entire British garrison of 11,000 soldiers and sailors plus over 1,000 Loyalist refugees evacuated by sea, never to return. The successful siege was the first major American victory of the war and demonstrated Washington's capacity for strategic patience and bold action.