In 1942, a stretch of Illinois prairie that had served as a battleground and a railroad depot became the site of a major manufacturing plant, producing Douglas C-54 Skymasters for World War II. Less than twenty years later, that plot of land boasted the biggest and busiest airport in the world. Many of the millions who have since passed through it have likely only regarded it as a place between cities. But for people like Michael Branigan, who has spent years on its tarmac, they know that O'Hare is a city unto itself, with a fascinating history of gangsters and heroes, mayors, presidents and pilots.