Greater Chicago Area
The Chicago Metropolitan Statistical Area (MSA) was originally designated by the United States Census Bureau in 1950. It consisted of the Illinois counties of Cook, DuPage, Kane, Lake and Will, along with Lake County in Indiana. As surrounding counties saw an increase in their population densities and the number of their residents employed within Cook County, they met Census criteria to be added to the MSA. The Chicago MSA, now defined as the Chicago-Naperville-Elgin, IL-IN-WI Metropolitan Statistical Area, is the third largest MSA by population in the United States with a population of 9,554,598 (2014 estimate).