On August 19, 1775, Lieutenant Colonel Francis Smith, under the orders of British General Thomas Gage, secretly led a large group of British troops to the town of Concord, Massachusetts, with the purpose of destroying the Massachusetts militia's store of arms and military supplies. Patriot organizers learned of the expedition and moved the stores to safe locations. The local militia, the Minutemen, faced the British at Lexington early in the morning on April 19th, but were outnumbered; they retreated after a brief firefight. The Minutemen attacked again at Concord and forced the British to retreat, with Patriots inflicting heavy casualties on the British as they marched back to Boston. The conflicts initiated the Siege of Boston, and are considered the first battles of the American Revolution. After the skirmish, the Massachusetts Provincial Congress ordered the taking of official depositions from many witnesses present at the fight, in order to establish that the British fired the first shot. The question of which side fired the opening salvo is still unanswered.
From the guide to the Lexington and Concord collection, 1775, (William L. Clements Library, University of Michigan)