Chicago

Chicago was a city in the state of Illinois in the United States on Earth. It was noted for having been home to many gangsters in the 1920s. The Seventh Doctor and Ace went to Chicago and met Dekker. (NA: Blood Harvest)

In 1931, the Master lived in Chicago as gangster Duke Dominus, but his plan was unknowingly defeated by the Fourth Doctor. (VD: The Duke of Dominoes)

In 1940, Cody McBride left his home town of Chicago for London. (PDA: Illegal Alien)

In 2006, the First Doctor, Susan, Ian Chesterton, and Barbara Wright arrived in Chicago in the TARDIS and started a cross-country trip there. Afterwards, they returned to Chicago by aeroplane. (ST: The Mother Road‎)