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American Revolution in Massachusetts

An overview of Massachusetts' history during America's Revolutionary Era.

March-June 1776: Fortification, Evacuation, and the Aftermath


Knox leading artillery train

A plan to break the siege of Boston centered on fortifying Dorchester Heights, a strategically valuable high point in what is now South Boston, using 60 tons of canons and other armaments from British-held Fort Ticonderoga in Upstate New York. The fort and all of its armaments were captured on May 10, 1775 in a mission led by Benedict Arnold along with Ethan Allen and the Green Mountain Boys.

It was decided that the armaments should not be moved until the winter, when the frozen ground and snow would make it easier to move the large and heavy artillery. Henry Knox was tasked with leading an expedition to bring the armaments from Fort Ticonderoga to Boston. The expedition left Ticonderoga on November 17, 1775 and began arriving in the Boston area on January 25, 1776.


Washington at Dorchester Heights, Emanuel Leutze (1852)

Some of the armaments were used to fire on Boston from Cambridge and Roxbury in order to distract the British forces while preparations for the fortification of Dorchester Heights were underway. Dorchester Heights was finally fortified during the night of March 4 into March 5, led by Brigadier General John Thomas with a force of 800 soldiers and 1,200 workers. The construction noises were hidden by the noise of further bombardments.

General Howe, upon being made aware of the fortifications, first launched a failed barrage of cannon fire against the heights.  He then planned an assault on Dorchester Heights. Washington had already planned and prepared countermeasures to an assault, and increased the number of soldiers on the Dorchester line to nearly 6,000.  

A snowstorm that developed late in the day on March 5th lasted for several days and delayed Howe’s planned assault. By the time the storm was over Howe had reconsidered, deciding that it would be better to save his forces for other battles rather than deplete them trying to hold Boston. A unsigned letter was sent to Washington's position on March 8, saying that Boston would not be destroyed so long as the British were allowed to leave without interference. Although Washington did not formally acknowledge the letter, he did allow the British to leave Boston unmolested.


Lord Howe Evacuating Boston (Library of Congress)

On March 17, after further delays caused by bad weather and unfavorable winds, British forces finally began evacuating Boston. The eight-year long occupation of Boston ended as 120 ships carrying about 11,000 people were on their way out of the harbor by 9AM.

The British would destroy Fort William on Castle Island during the evacuation, forcing the Americans to build their own fortifications on the island. Howe also left behind several ships in the harbor, mainly to divert vessels heading into Boston. These ships remained until June 13, 1776, when a barrage from canon placed on the harbor islands drove them away. On their way out, a boat carrying a timed charge was sent ashore to Little Brewster Island and exploded, destroying the light house.


Boston from Dorchester Heights, E.T. Coke (c. 1830-1839)

General Howe, although heavily criticized for the failure of the Boston Campaign, retained his command for two more years.

Many Massachusetts Loyalists opted to leave with the British, either returning to England or settling in Canada. Some would come back to Massachusetts after the war ended but many would stay where they had settled in Nova Scotia and New Brunswick.

After the evacuation Boston ceased to be a military target although it retained its importance as a center of activity during the war. New England itself would see relatively little military action for the rest of the war, with the focus shifting to New York, New Jersey, and Philadelphia.


Dorchester Heights Monument

From 1926 to 1927 New York and Massachusetts placed markers along the route taken by the artillery train in commemoration of the 150th anniversary of the expedition, calling it the Henry Knox Trail. 

Evacuation Day began being celebrated in 1901, and was made an official holiday for Suffolk County in Massachusetts in 1938. The parade held on or around that day in South Boston every year is meant to also commemorate Evacuation Day, as the route normally goes past Dorchester Heights.

A monument commemorating the fortification on Dorchester Heights was erected in 1902. Dorchester Heights was also added to the National Register of Historic Places in 2001, and is now overseen by the National Park Service.
 


Dorchester Heights fortifications