After Bunker Hill, the British army held Boston and the Continental Army held everything around it, a standoff that lasted nearly nine more months with neither side able to force the issue. What finally broke the deadlock was not a battle but an overnight construction project: on the night of March 4, 1776, Washington's troops fortified Dorchester Heights with cannon hauled three hundred miles from Fort Ticonderoga, putting the British fleet and the city itself within range of American guns. Within two weeks the British had abandoned Boston entirely. Washington's own letters describing both the maneuver and its aftermath survive at Founders Online, along with the Boston selectmen's letter of thanks and his reply to it.
Washington took formal command of the army surrounding Boston on July 3, 1775, inheriting a force that had bottled up the British garrison since the fighting at Lexington and Concord in April. For months neither side could break the stalemate. The British, reinforced by sea, held the city and harbor. The Continental Army, short on gunpowder and lacking the heavy artillery needed to threaten British positions directly, could do little more than maintain the encirclement. Washington needed guns he did not have, and in November 1775 he found a source: the cannon captured at Fort Ticonderoga the previous May, sitting unused at the southern end of Lake Champlain.
Washington ordered Henry Knox, a young Boston bookseller turned artillery officer, to retrieve them. Over the following two months Knox's team hauled 59 cannon, roughly sixty tons of artillery, by sled across frozen rivers and the Berkshire Mountains, arriving in Cambridge in late January 1776. Washington now had the means to force the issue. What he needed was a position from which those guns could actually threaten the city.
Dorchester Heights, high ground south of Boston overlooking both the city and the harbor, had sat undefended for most of the siege. On the night of March 4, more than a thousand soldiers and volunteers moved up the hill under cover of a diversionary bombardment elsewhere in the lines, hauling tools and prefabricated fortification materials by oxcart. By dawn on March 5, the sixth anniversary of the Boston Massacre, a fortified position bristling with cannon stood where there had been nothing the evening before. British General William Howe now faced the same threat Washington had faced for months in reverse: an enemy position commanding the harbor that he could not simply ignore.
Howe's officers had little confidence the British fleet anchored in the harbor could survive if American guns stayed on Dorchester Heights. Howe began preparing an assault on the position reminiscent of Bunker Hill the previous June, but a violent storm disrupted his plans before troops could be landed. With his only alternative to evacuation taken away by the weather, Howe chose to abandon the city.
The evacuation itself was hurried and disorderly. Roughly 170 ships crowded Boston Harbor to carry off some 11,000 people, soldiers, Loyalist civilians, and their families, bound for Halifax, Nova Scotia. British soldiers barricaded streets, spiked cannon they could not transport, and in several documented cases plundered homes and shops on their way out. A Continental officer watching from the lines that morning recorded what he saw the moment word reached the American positions.
This Morning we had the Agreable Sight of a Number of Ships leaving the Town of Boston with a large Number of Boats full of Soldiers, about ten of Clock several Lads came to our out Centries and informed us that the Troops had intirely left the Town.
Washington entered the city soon after and wrote to his brother two weeks later describing the condition of the British troops who had left.
By all accounts there never existed a more miserable set of beings than these wretched creatures now are.
The British had left behind a substantial quantity of supplies and weaponry in their haste, a detail Washington reported in several letters written in the days immediately following the evacuation.
The hurry in which they have Imbark'd is inconceivable, they have not, from a rough estimate, left less than 30,000 pounds worth of his Majestys Property behind them, in Provisions and Stores, Vessels, Rugs Blankets, near 30 pieces of fine heavy Cannon are left, spiked, which we are now drilling, a Mortar or two, Shott Shells in abundance, all their Artillery Carts, Powder Waggons.
Boston's selectmen wrote to Washington shortly after the evacuation, thanking him formally on behalf of the town for what the siege's end had spared them.
You have not only saved a large, elegant, and once populous City, from total Destruction, but relieved the few wretched Inhabitants from all the Horrors of a besieged Town, from the Insults and Abuses of a disgraced and chagrined Army, and restored many Inhabitants to their quiet Habitations who had fled, for Safety, to the Bosom of their Country.
Washington's reply was equally formal, and notably warm for a man not given to florid language in his official correspondence. Abigail Adams, writing to her husband John from just outside the city, captured something closer to the disbelief many residents felt that the siege had ended as it had, with the city itself still standing.
The more I think of our Enemies quitting Boston, the more amazed I am, that they should leave such a harbour, such fortifications, such intrenchments, and that we should be in peaceable possession of a Town which we expected would cost us a river of Blood without one Drop shed. Surely it is the Lords doings and it is Marvelous in our Eyes.
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