Meanwhile, as the Continental Congress gathered in Philadelphia in September 1774, Massachusetts was also defying British authority. In August, a Middlesex County Congress had urged Patriots to close the existing royal courts and to transfer their political allegiance to the popularly elected House of Representatives. Subsequently, armed crowds harassed Loyalists and ensured Patriot rule in most of New England.

In response, General Thomas Gage, now the military governor of Massachusetts, ordered British troops in Boston in September 1774 to seize Patriot armories in nearby Charlestown and Cambridge. An army of 20,000 militiamen quickly mobilized to safeguard other Massachusetts military depots. The Concord town meeting raised a defensive force, the famous Minutemen, to “Stand at a minutes warning in Case of alarm.” Increasingly, Gage’s authority was limited to Boston, where it rested on the bayonets of his 3,500 troops. Meanwhile, the Patriot-controlled Massachusetts assembly met in nearby Salem in open defiance of Parliament, collecting taxes, bolstering the militia, and assuming the responsibilities of government.

In London, the colonial secretary, Lord Dartmouth, proclaimed Massachusetts to be in “open rebellion” and ordered Gage to march against the “rude rabble.” On the night of April 18, 1775, Gage dispatched 700 soldiers to capture colonial leaders and supplies at Concord. However, Paul Revere and a series of other riders warned Patriots in many towns, and at dawn, militiamen confronted the British regulars first at Lexington and then at Concord. Those first skirmishes took a handful of lives, but as the British retreated to Boston, militia from neighboring towns repeatedly ambushed them. By the end of the day, 73 British soldiers were dead, 174 wounded, and 26 missing. British fire had killed 49 Massachusetts militiamen and wounded 39. Twelve years of economic and constitutional conflict had ended in violence.