American Revolutionary War: Following the Battles of Lexington and Concord, the Siege of Boston begins with American militias blocking land access to the British-held city.

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.

April 19 is the 109th day of the year in the Gregorian calendar; 256 days remain until the end of the year.