The beginning of the end of the Siege of Boston

In early March of 1776, British troops, Loyalists, and Bostonians without the resources to leave had been under siege within city limits for nearly a year, hobbled by outbreaks of disease and with shortages of fuel, food and other necessities a daily reality. Supply lines had been cut off by land and hampered at sea by patriot troops led by George Washington from his headquarters in Cambridge. The unsustainability of the British position in Boston had long been recognized; when William Howe replaced Thomas Gage in October of 1775 his goal was merely to hold Boston until they could remove to New York where the Loyalist community was stronger and the harbor deeper. As Allen French wrote in The First Year of the American Revolution,

From Gage down all acknowledged that the army was helpless in Boston. April 19 and Bunker Hill had taught the impossibility of conquering the New Englanders, fighting by their chosen methods in that country of rolling hills, winding roads, stone walls, and much cover.

Henry Knox’s artillery train

Unfortunately for Washington and his troops, the ability to drive the British out of Boston once and for all was also hampered by a lack of supplies. That is, until a Boston bookseller turned Colonel named Henry Knox undertook a remarkable expedition to take possession of cannon and mortars from Fort Ticonderoga and bring them back to Massachusetts in the winter of 1776. This arduous journey is recounted in his journal in the collections of the MHS.

Once the armaments arrived (totally unremarked by the British), Washington ordered their installation on Dorchester Heights. With its commanding view of both harbor and town, Dorchester Heights had been coveted by both sides of the conflict. Washington strategically placed some of the cannon at other locations along the siege lines and began nightly bombardments as a diversion for the real mission. On the night of 4 March 1776 some 2,500 men led by General John Thomas silently climbed the Heights, building fortifications and placing cannon aimed squarely at the British position. When he observed their work the next day—the anniversary of the Boston Massacre--British General William Howe is said to have commented “the rebels have done more in one night than my whole army would have done in a month." The blindsided Howe immediately planned a retaliatory strike on Dorchester, but this plan, stymied by a raging snowstorm, would soon be replaced by one to evacuate Boston entirely.

On 8 March, Timothy Newell and three other Boston selectmen, who had been forbidden to leave Boston, crossed the lines at Boston Neck with a white flag and a promise that General Howe had “no intention of destroying the town, unless the troops under his command are molested during the embarkation.” As described by David McCullough in his 1776, the morning of 17 March 1776 was

… a spectacle such as could only have been imagined until that morning. There were 120 ships departing with more than 11,000 people packed on board—8,906 King’s troops, 667 women and 553 children, and in addition, waiting down the harbor, were 1,100 Loyalists.

As he had promised, Howe did not set fire to the town on his way out, but did destroy munitions and other supplies that could be of use.

Next steps

As Washington suggests in his letter to Brigadier General Clinton, the next target for the British would be New York, but the ships leaving Boston on that March morning laid at anchor off the Massachusetts coast for 10 days before heading for Halifax, Nova Scotia. The British would take New York City in the summer of 1776 and remain there for the duration of the war. Although it would be seven long years before independence—and peace—came to the colonies, Boston and New England were largely spared further ravages of war.

New exhibit at the Massachusetts Historical Society

As the British troops evacuated Boston, the real work of independence was already underway. A landmark exhibition 1776: Declaring Independence opens at the Society’s headquarters on 6 March 2026. View private letters, intimate diaries, and rare handwritten drafts of the Declaration of Independence by John Adams and Thomas Jefferson and discover how abstract ideas about liberty, loyalty, and the role of government coalesced into our founding document. Click here for gallery hours and other important information.