Northern Illinois in the context of "Illinois Route 64"

St. Clair County is the ninth most populous county in Illinois. Located directly east of St. Louis, the county is part of the Metro East region of the Greater St. Louis metropolitan area in southern Illinois. As of the 2020 United States census, St. Clair County had a population of 257,400, making it the second most populous county in Illinois outside the Northern Third. Belleville is the county seat and largest city.

Along the Mississippi River, Cahokia Village was founded in 1697 by French settlers and served as a Jesuit mission to convert tribes of the Illinois Confederation to Christianity. The area became the center of the French Illinois Country. Prior to the establishment of Illinois as a state, the government of the Northwest Territory created St. Clair County in 1790. In 1809, the county became the administrative center of the Illinois Territory and one of the two original counties of Illinois, alongside Randolph County. In 1970, the United States Census Bureau placed the mean center of U.S. population, which generally has moved west every decennial census, in St. Clair County.

Rockford is a city in Winnebago and Ogle counties in the U.S. state of Illinois. It is located in far northern Illinois on the banks of the Rock River. The fifth-most populous city in Illinois with a population of 148,655 at the 2020 census, it anchors the Rockford metropolitan area with 337,000 residents. Rockford is the county seat of Winnebago County and the most populous city in Illinois outside the Chicago metropolitan area.

Settled in the mid-1830s as Midway, Rockford became strategic for industrial development, stemming from its location roughly equidistant between Lake Michigan and the Mississippi River. During the second half of the 19th century, it became notable for its production of heavy machinery, hardware, and tools. At the beginning of the 20th century, the city was the second leading center of furniture manufacturing in the U.S. During the second half of the 20th century, Rockford struggled alongside many Rust Belt cities to maintain its previous industrial presence. Since the late 1990s, efforts in economic diversification have led to the growth of automotive, aerospace, and healthcare industries, as well as the undertaking of various tourism and downtown revitalization efforts.

The Rust Belt, formerly the Steel Belt or Factory Belt, is an area of the United States that underwent substantial industrial decline in the late 20th century. The region is centered in the Great Lakes and Mid Atlantic regions of the United States. Common definitions of the Rust Belt include Ohio, Indiana, Northern Illinois, southeastern Wisconsin, Michigan, Pennsylvania, and Upstate New York. Some broader geographic definitions of the region include parts of Central Illinois, Iowa, Kentucky, Maryland, Minnesota, Missouri, New Jersey, and West Virginia. The term "Rust Belt" is considered to be a pejorative by some people in the region.

Between the late 19th century and late 20th century, the Rust Belt formed the industrial heartland of the country, and its economies were largely based on iron and steel, automobile manufacturing, coal mining, and the processing of raw materials. The term "Rust Belt", derived from the substance rust, refers to the socially corrosive effects of economic decline, population loss, and urban decay attributable to deindustrialization. The term gained popularity in the U.S. beginning in the 1980s, when it was commonly contrasted with the Sun Belt, whose economy was then thriving.