When British Army activity on April 7, 1775 suggested the possibility of troop movements, Joseph Warren sent Revere to warn the Massachusetts Provincial Congress, then sitting in Concord, the site of one of the larger caches of Patriot military supplies. After receiving the warning, Concord residents began moving the military supplies away from the town.
Riding through present-day Somerville, Medford, and Arlington, Revere warned patriots along his route, many of whom set out on horseback to deliver warnings of their own. By the end of the night there were probably as many as 40 riders throughout Middlesex County carrying the news of the army’s advance. The alarm raised by the three riders successfully allowed the militia to confront the British troops in Concord, and then harry them all the way back to Boston.