This charming map published in July 1775 narrates the events that sparked the American Revolution, the battles of Lexington and Concord (April 18, 1775). The city of Boston may be found at the center of the map on a small peninsula surrounded by British warships. (Further detail about Boston itself may be found on Core map A). The immediate cause of the famous battles was the decision by General Thomas Gage, the commander in chief of British forces in North America, to confiscate stores of gunpowder and weapons kept in Concord by the Massachusetts Provincial Congress.

The force commanded by Lieutenant Colonel Francis Smith, set out from Boston on the night of April 18. Under the cover or darkness, the British force crossed the Charles River, landing on the mainland east of Cambridge. Unfortunately for them, militia forces had been warned of their mission by dispatch riders Paul Revere and William Dawes and by Dr. Samuel Prescott, a doctor from Concord. Members of the local militia quickly gathered from nearby towns to intercept the British forces. Some of these "minutemen" may be seen at the top of our map, on the March from Woburn and Salem. In what is regarded as the first skirmish of the American Revolution, a small company of colonial militia briefly (and accidentally) clashed with an advance column of British soldiers commanded by Major John Pitcairn in Lexington. This action temporarily halted the British March, and by the time they reached Concord, the Americans had hidden most of the military stores the British were after and had taken up a defensive position at the North Bridge. The map depicts the ensuing skirmish at upper left. Alarmed by the danger he now felt all around his command, Smith ordered a return to Boston about midday. The retreat was a disaster for the British. Marching the middle of the main road, Smith's force was harassed every step of the way by small contingents of Massachusetts militiamen who fired at the column from the cover of the surrounding forest. Smith's force was saved by its encounter with reinforcements under the command of Lord Hugh Percy at Lexington, but the militia kept up the pressure all the way to Charlestown, where the British force at last recrossed to the safety of Boston.

In all, 273 British soldiers were wounded, killed, or missing, against only 95 militia casualties. More importantly, the day's events galvanized opinion against the British military presence in New England. Within days, Massachusetts organized a volunteer army and placed it under the command by General Artemis Ward (shown in camp at Water Town Hill on the Charles River at left center on the map). Forces from other New England colonies soon joined this army, including the Connecticut forces of General Israel Putnam (encamped on the Mistick (Mystic) River). The British forces in Boston were now besieged, and the American Revolution begun in earnest.