In the autumn of 1775, the Continental Army found itself in a frustrating stalemate outside Boston. General George Washington's forces had successfully contained the British within the city following the battles of Lexington, Concord, and Bunker Hill, but lacked the heavy artillery necessary to drive them out. The solution to this predicament would come from an unlikely source: a 25-year-old Boston bookseller turned artillery officer named Henry Knox, whose ambitious proposal would launch one of the most remarkable logistical achievements of the Revolutionary War.