Ashburn Flying Field was the first airport built to serve Chicago, Illinois.

Chicago Tribune is a major newspaper that serves Chicago, Illinois.

Ameritech already serves Chicago and Detroit, which are third and fifth, respectively, in terms of potential customers.

The system serves Chicago and its metropolitan area through 241 stations on 11 different rail lines.

It serves northwest Indiana and south suburban Chicago.

Early plans for the airline called for it to serve Appleton, Chicago, and Atlanta.

Others, like those serving New York City and Chicago, have suffered a form of gridlock.

In 2013 it began serving Boston, Brooklyn and Chicago as well.

Iberia, one of Europe's leading carriers, also serves Chicago and Los Angeles.

Divvy is a bicycle sharing system that will serve Chicago beginning in Summer 2013.