[7] Fueled by the economy of Chicago, the Chicago metropolitan area is home to many of the United States' largest companies, including Abbott Laboratories, AbbVie Inc., Allstate, Baxter International, Conagra, Crate and Barrel, Kraft Heinz, McDonald's, CNH Industrial, GE Healthcare, Aon PLC, Willis Towers Watson, Mondelez International, Motorola, United Airlines, US Foods, Walgreens, and more.

Most of the state of Illinois lies outside the Chicago metropolitan area and inside the North American Corn Belt.

[14] Manufacturing in Illinois accounts for 14% of the state's total output and generates $101 billion in economic activity.

A key piece of infrastructure for several generations was the Union Stock Yards of Chicago, which from 1865 until 1971 penned and slaughtered millions of cattle and hogs into standardized cuts of beef and pork.

[16][17] Governor Peter Altgeld had made Florence Kelley the Chief Factory Inspector for the state of Illinois.

[16][19] After Governor Altgeld was not re-elected in 1896 and Kelley was removed from her position, flagrant violations of the child labor provision were reported.

[16] The centralized location of Illinois made it a key manufacturing hub, especially for farm machinery and specialty motor vehicles.

In downstate Illinois, the John Deere Company became one of the world's largest makers of farm machinery, and Caterpillar achieved similar dominance in its diversified line of off-road vehicles.

[citation needed] The Chicago area, meanwhile, began to produce significant quantities of telecommunications gear, electronics, steel, automobiles, and industrial products.

[23] By the early 2000s, Illinois's economy had moved toward a dependence on high-value-added services such as financial trading, higher education, logistics, and medicine.