Dawes, who was known and trusted by Sons of Liberty leader Dr. Joseph Warren, was assigned by Warren to ride from Boston to Lexington, Massachusetts, on the night of April 18, 1775, when it became clear that a British column was going to march into the countryside. Dawes' mission was to warn John Hancock and Samuel Adams that they were in danger of arrest. Dawes took the land route out of Boston through the Boston Neck, leaving just before the British military sealed off the town.