Depending on who you ask it is and has been already considered "Chicagoland."
"Chicagoland" is an informal name for the Chicago metropolitan area used primarily by copywriters, advertising agencies, and traffic reporters. There is no precise definition for the term "Chicagoland"; the Chicago Tribune, which coined the term, includes the city of Chicago, the rest of Cook County, eight nearby Illinois counties; Lake, McHenry, DuPage, Kane, Kendall, Grundy, Will and Kankakee, and two counties in Indiana; Lake and Porter. The Illinois Department of Tourism defines Chicagoland as Cook County without the city of Chicago, and only Lake, DuPage, Kane and Will counties. The Chicagoland Chamber of Commerce defines it as all of Cook, and DuPage, Kane, Lake, McHenry and Will counties.
The term was popularized by the Chicago Tribune. Colonel Robert R. McCormick, editor and publisher, usually gets credit for placing the term in common use. McCormick's conception of Chicagoland stretched all the way to nearby parts of Iowa and Michigan. The first usage came on July 27, 1926 (page 1) with the headline: "Chicagoland's Shrines: A Tour of Discoveries" by reporter James O'Donnell Bennett. He claimed that Chicagoland comprised everything in a 200 mile radius in every direction and reported on many different places in the area. The Tribune was the dominant newspaper in a vast area stretching to the west of the city, and that hinterland was closely tied to the metropolis by rail lines and commercial links.
The Chicago metropolitan area is the metropolitan area associated with the city of Chicago in the United States. It is the area that is closely linked to the city through social, economic, and cultural ties. There are several definitions of the area, the two most common being the area under the jurisdiction of the Chicago Metropolitan Agency for Planning (a metropolitan planning organization), and the area defined by the federal Office of Management and Budget (OMB) as the Chicago-Naperville-Joliet, IL-IN-WI Metropolitan Statistical Area. The metropolitan area is also informally known by residents as Chicagoland.
UPDATE! Wow you post up historical data and people say your a bunch of bull. Okay one more add to this.... The departments of transportations of Illinois, Wisconsin and Indiana has already planned for the whole Gary-Chicago-Milwaukee Corridor expansion which you can read at http://www.gcmtravel.com/gcm/home.jsp.
While sure there is a rivalry, did anyone expect Chicagoland to include Aurora or other places that are now apart of it. I answer a question with details that are true. There is a connection with all these places. The idea is happening. I am not pro or against. But if you want to challenge my data find data against it!