Date: April 18-19, 1775 On the night before the Battles of Lexington and Concord, Paul Revere and William Dawes left Boston to warn the countryside that the British Regulars were on the march. In particular, they wanted to warn John Hancock and Samuel Adams that the Regulars intended to arrest them. Revere left Boston by boat across the Charles River, taking the road across the Charlestown peninsula. Dawes took the longer land route across Boston Neck. Revere arrived in Lexington first, but Dawes wasn't far behind.