Dorchester Heights & Evacuation Day: Freeing the City of Boston

Fortifications on Dorchester Heights

MA Evacuation Day Celebration March 17, 1901
MA Evacuation Day Celebration March 17, 1901. Courtesy The Boston Society | Old State House

Here is a fun question for you!

Why do many school children in Boston have March 17th, or St. Patrick’s Day, off from school? Believe it or not, it has nothing to do with the popular Saint’s holy day, but instead celebrates Evacuation Day.

After the fledgling Continental Army lost the Battle of Bunker Hill and Breed’s Hill, the Continental Congress put General George Washington in charge of breaking the Siege of Boston. He needs to drive the British out of Boston, but how? The British troops suffered heavy losses for that hill, and a strike at the right time and with enough firepower could force a retreat.

Map of Boston and Vicinity, 1776
History Department, United States Military Academy, Public domain, via Wikimedia Commons

Dorchester Heights, located in what is now South Boston, had a perfect view of both Boston Harbor and downtown Boston, where many British soldiers were quartered. Being the highest point in the region, it provided a perfect place for an artillery unit, but where would they acquire enough artillery pieces? As in many times during history, this was a time of unlikely people accomplishing unlikely things. Enter Henry Knox, son of immigrants from Scotland, bookseller, brawler, and military history enthusiast. He joined local militias and was skilled with artillery. He was also a member of the Sons of Liberty. Knox impressed Washington with the way he fortified artillery positions in Roxbury.

Henry Knox Portrait
Henry Knox Portrait. Courtesy of

Knox was well-read and had just the idea for fortifications on Dorchester Heights – he convinced Washington to let him acquire the cannons seized from the British at Fort Ticonderoga. His plan was to drag the cannon on sleds across many miles of frozen ground, including river crossings and through the Berkshire Mountains. This was no small undertaking–Knox thought he could manage it in two weeks, but because of weather conditions, the challenges of recovering cannon that sunk in river crossings, and the lack of available labor in sparsely settled land dragged (pun intended) the journey to ten weeks. Knox left Boston in November of 1775, and did not return with the cannon until the end of January. 

Now that the cannon had arrived, Washington needed to distract British forces and draw attention away from Dorchester Heights where General John Thomas and the Continental army began quietly building artillery fortifications in early March. So Washington directed some of the cannon to be placed in existing fortifications like Lechmere Point, Cobble Hill, and Lamb’s Dam in Roxbury.

Knot Trail Map
Knox Trail

Explore the Knox Trail!

Lechmere Point
Lechmere Point

“It took a little less than a month before the artillery battery at Lamb’s Dam started to exact casualties. On 6 October, Boston selectman Timothy Newell recorded:

The Provincials from Lams Dam discharged their cannon at the Regulars, as they relieve guard at the lines—One Corporal killed with a cannon ball.”

“Joshua Lamb built his dam (site of Northampton Street) about 1720 to protect his salt marsh and make basin for his salt pans. The tides slowed and ice formed in winter thus makings salt extraction easier. General Joseph Putnam established a salt works on the Neck about 1783.” 

Roxbury Fandom Wiki had this useful information 

Distracting Fire From Cambridge-Somerville-Roxbury
A map of George Washington's fortifications. Red circles denote some of the significant fortifications at Lechmere Point, Cobble Hill, and Lamb's Dam. Purple arrows show distracting fire to draw British attention away from the fortification operations at Dorchester Heights.

When the Enemy first discovered our Works in the morning, they seemed to be in great confusion…

General George Washington to President of the Continental Congress John Hancock, March 7-9, 1776

Where can we find these sites in Present-Day Massachusetts?

Some of these names may be familiar, and then again, some are no longer there, so it is understandable if you have never heard of them before.

Dorchester Heights was once two hills, but the second hill was used to fill in land in the neighborhood, the same as happened to numerous hills in the region. However, there is still a park there, as shown in our tour images.

Lechmere Point and Dorchester Heights
Lechmere Point and Dorchester Heights

If the name Lechmere Point sounds familiar, it isn’t surprising! Lechmere is a section of East Cambridge, named for a Loyalist landowner that fled at the beginning of the Revolution. Centuries later, it would also be the name for the famous local department store, founded where the CambridgeSide Galleria is. (See map above.)

Also Lechmere station on the Green Line of the MBTA.

Cobble Hill
Cobble Hill

Cobble Hill is in Somerville, or rather it was. Like many hills that once existed in Revolutionary War times, the hill was leveled in later years. 

…The hills of those old days are fast disappearing as well as the rivers, both in name and substance….Asylum Hill, which was the Miller’s Hill, or Cobble Hill of a hundred years or more ago, has the seal of destruction set upon it….

Samuels, pg. 22, 1897 – Internet Archive

When McClean’s Hospital relocated to Belmont, the mansion it was originally housed in, as well as the hill it stood upon, was razed. If you are looking for the area it once was, it is the region around the inner belt area of Somerville, the Cobble Hill apartments being located at the north end of where the hill once was. (see map above)

Northampton St - Lamb's Dam
Northampton St - Lamb's Dam

In 1796 the creek that Lamb’s Dam sat on was turned into the Roxbury Canal. Today this is the neighborhood slightly west and south of the Boston Medical Center.

Historians have worked to map out Henry Knox’s Trail as best as they can based on his diary (linked in the resources section) as well as historic maps that existed at the time showing roads connecting communities.

Cool Fact! The path that Knox took through Massachusetts, though somewhat speculative based on missing pages from his diary. It is thought however, that it generally followed the path now taken by the Mass Pike. I bet it is much easier to travel now, don’t you think?

What do you think was the hardest part of Colonel Knox’s journey with the artillery, and Why?
Do you notice any differences in the historic maps vs. the modern Google Maps of the regions? How is the shape of the land around Dorchester Heights different?
What do you think might have happened if there was not a storm in early March 1776 preventing General Howe from landing troops on Dorchester Point?
What surprised you most about this event?

This source includes excellent lesson materials produced by the National Park Service including activities, maps, and questions based on primary source material.

Normally, Wiki’s are not our chosen sources, however, this one has excellent information and is very readable.