The Chicago Fire Department (CFD) provides fire suppression and emergency medical services to the city of Chicago, under the Mayor of Chicago's jurisdiction. The CFD is the third largest fire department in the United States, just after FDNY and Cal Fire.
- Wallace Boden - Battalion Chief for Firehouse 51.
- Kelly Severide - Lieutenant Officer for Squad 3.
- Matthew Casey - Captain of Firehouse 51 and Lieutenant of Truck 81