In March 1776, after an 11-month siege of Boston, British troops woke up to find a fortified American position above the city that had not been there the night before. This episode explains how the Continental Army ended the siege without a major battle, through hard work, engineering, deception, and a lucky storm.

We follow Henry Knox’s 300-mile winter journey hauling 60 tons of artillery from Fort Ticonderoga, Rufus Putnam’s prefabricated chandeliers and fascines for frozen ground, the decoy bombardments, and the hay bales that muffled the night march. Then we look at General William Howe’s planned assault, the nor’easter that stopped it, and the British evacuation on March 17, now celebrated as Evacuation Day.

• Why the memory of Bunker Hill made both sides hesitant to seize the high ground
• How Knox moved cannon on sledges across mountains and frozen rivers
• Abatis, rock-filled barrels, and Washington’s plan to strike Boston by boat if Howe attacked
• Howe’s reaction to the overnight fortress and the Royal Navy’s sudden danger
• How the heights were later leveled for landfill and how Evacuation Day falls on St. Patrick’s Day