The final installment of Ric Burns's documentary about New York tells the history of the World Trade Center, from the optimistic post-World War II economy that spurred the major construction project to the towers' tragic fall on Sept. 11, 2001. Rare archival footage and in-depth interviews with experts help chronicle the story of the skyscrapers. The program also looks at the city's efforts to recover and rebuild after the 2001 terrorist attacks.