Lake Champlain, 125 miles long, flows north into the Richelieu River and then the St. Lawrence River, while from Ticonderoga it extends 25 miles south to its end near present-day Whitehall, New York. During the 18th century, the region’s rivers and lakes functioned as the interstate highways of their time, and control of these waterways meant control of the surrounding territory. Lake Champlain was a key link in the network connecting Quebec City to the north with New York City to the south. Fort Ticonderoga guarded the portage to Lake George, four miles away beyond Mount Defiance, and the main route south from Ticonderoga was to cross overland to Lake George, sail its 32-mile length, and then portage 12 miles to the Hudson River at Fort Edward. Mount Defiance, rising nearly 900 feet about a mile to the southwest, was Fort Ticonderoga’s Achilles heel, and during the American Revolution British forces under Lieutenant-General John Burgoyne placed artillery on its summit, forcing the startled American army under Major General Arthur St. Clair to evacuate Ticonderoga and Mount Independence on July 5, 1777, which allowed the British to retake the fort two years after it had fallen to the Americans. Mount Independence, on the Vermont shore, was cleared and fortified by American forces in the summer and fall of 1776 to strengthen Fort Ticonderoga against an anticipated British attack from Canada, and by October 1776 about two-thirds of the American troops at Ticonderoga were encamped there.