In late 1775, George Washington faced a dilemma. The British were bottled up in Boston, but he lacked the heavy artillery needed to bombard them. He knew Patriot forces had recently captured Fort Ticonderoga and Crown Point in northern New York, along with scores of cannons, mortars and howitzers. Washington sent Henry Knox, a 25-year-old Boston bookseller whose knowledge of artillery came from paging through his own inventory, to fetch them.

Knox's expedition became the most consequential road trip in American history. He transported 60 tons of weaponry across 300 miles of snowy wilderness and icy lakes—from northern New York to Cambridge, Massachusetts. Armed with £1,000 (about $193,000 today), he floated weapons down lakes before they froze, then towed them overland on wooden sleds, climbed mountains and built carriages. The成功了 enabled Washington to place artillery on Dorchester Heights, forcing the British to evacuate.

In 1926, for the sesquicentennial, New York and Massachusetts installed roughly 60 historical markers along Knox's route. Journalist Richard Rubin recently retraced the journey in four days by car, finding markers in cities, suburbs, small towns and countryside—each marking where colonial upstarts first began thinking of themselves as Americans rather than just New Yorkers or "Massachusites."