Chicago, City (pop., 2010: 2,695,598), northeastern Illinois, U.S. Located on Lake Michigan and the Chicago River, Chicago has extensive port facilities. In the 17th century the name was associated with a portage between the Des Plaines and Chicago rivers connecting the St. Lawrence River and the Great Lakes with the Mississippi River. Fort Dearborn was built in the early 1800s on a tract acquired from Native Americans. It expanded rapidly after the completion of the Illinois and Michigan Canal (1848)—which connected Lake Michigan to the Illinois River and thereby to the Mississippi—and also became the nation’s chief rail centre. Rebuilt quickly after a hugely destructive fire in 1871, it was the site of the World’s Columbian Exposition in 1893. It was the birthplace of the steel-frame skyscraper in the late 19th century, and it boasts designs by eminent architects, including Louis H. Sullivan, Frank Lloyd Wright, and Ludwig Mies van der Rohe. Nuclear scientists produced the first nuclear chain reaction at the University of Chicago in 1942. After World War II the city underwent another building boom, but, as in other large cities, its population subsequently dropped as its suburbs grew. The third largest U.S. city, it is a major industrial, commercial, and transportation centre and is the site of the Chicago Mercantile Exchange and the Chicago Board of Trade. Several museums and the Art Institute of Chicago are located there.
