Chelsea is a city in Suffolk County, Massachusetts, United States, directly across the Mystic River from Boston. At the 2020 census, Chelsea had a population of 40,787, making it the second most densely populated city in Massachusetts, behind Somerville. With a total area of 2.46 square miles (6.4 km2), Chelsea is the smallest city in Massachusetts in terms of total area. It is the city with the second-highest percentage of Latino residents in Massachusetts, behind Lawrence.

The siege of Boston was the opening phase of the American Revolutionary War. In the siege, American patriot militia led by newly-installed Continental Army commander George Washington prevented the British Army, which was garrisoned in Boston, from moving by land. Both sides faced resource, supply, and personnel challenges during the siege. British resupply and reinforcement was limited to sea access, which was impeded by American vessels. The British ultimately abandoned Boston after eleven months, moving their troops and equipment north, to Nova Scotia.