Chicago is the principle location of Watch Dogs. It is the largest city in the state of Illinois, and the third largest city in the United States. Ubisoft has stated that the in-game version of Chicago will be large enough to support vehicles that can travel in excess of 180mph. All the trailers thus far have taken place in Chicago, with the E3 Gameplay Video prominently featuring the Chicago River, the Ambrose Theater, and The Loop.
Chicago is linked by a massive public transport system run by the Chicago Transit Authority consisting of buses and trains, which in cooperation with the various Taxi cabs throughout the city, provide the most effective and rapid transport in the entire city. The city also houses two airports, though it is unclear whether or not they will be featured in the game.