The Battles of Lexington and Concord was the first major military campaign of the American Revolutionary War, resulting in an American victory and outpouring of militia support for the anti-British cause. The battles were fought on April 19, 1775, in Middlesex County, Province of Massachusetts Bay, within the towns of Lexington, Concord, Lincoln, Menotomy (present-day Arlington), and Cambridge. They marked the outbreak of armed conflict between the Kingdom of Great Britain and America's thirteen colonies.

About 700 British Army regulars in Boston, under Lieutenant Colonel Francis Smith, were given secret orders to capture and destroy Colonial military supplies reportedly stored by the Massachusetts militia at Concord. On the night before the battle, warning of the British expedition had been rapidly sent from Boston to militias in the area by several riders, including Paul Revere and Samuel Prescott, with information about British plans.

The first shots were fired just as the sun was rising at Lexington were. Eight militiamen were killed. The British suffered only one casualty. The militia was outnumbered and fell back, and the regulars proceeded on to Concord, where they broke apart into companies to search for the supplies. At the North Bridge in Concord, approximately 400 militiamen engaged 100 regulars from three companies of the King's troops at about 11:00 am, resulting in casualties on both sides. The outnumbered regulars fell back from the bridge and rejoined the main body of British forces in Concord. Gunfire continued throughout the day as the regulars marched back towards Boston. Lt. Col. Smith's expedition was rescued by reinforcements under Brigadier General Hugh Percy. The combined force of about 1,700 men reached the safety of Charlestown. The accumulated militias then blockaded the narrow land accesses to Charlestown and Boston, starting the siege of Boston.