Chicago is the most populous city in the U.S. state of Illinois and in the Midwestern United States. Located on the western shore of Lake Michigan, it is the third-most populous city in the United States and the fifth-most populous city in North America, with a population of 2.74 million at the 2020 census. The Chicago metropolitan area has approximately 9.62 million residents according to the 2020 census and is the third-largest metropolitan statistical area in the country and part of the fourth-largest combined statistical area in the United States, spanning 19 counties in three states and with a population of nearly 10 million. Chicago is the county seat of Cook County, the second-most populous county in the U.S.
Chicago was incorporated as a city in 1837 near a portage between the Great Lakes and the Mississippi River watershed. It grew rapidly in the mid-19th century. In 1871, the Great Chicago Fire destroyed several square miles and left more than 100,000 homeless, but Chicago's population continued to grow. Chicago made noted contributions to urban planning and architecture, such as the Chicago School, the development of the City Beautiful movement, the steel-framed skyscraper, and the Willis Tower being ranked among the tallest buildings in the Western Hemisphere.
Chicago is an international hub for finance, culture, commerce, industry, education, technology, telecommunications, and transportation. It has the largest and most diverse finance derivatives market in the world, generating 20% of all volume in commodities and financial futures alone. O'Hare International Airport was ranked the busiest airport in the world by number of take offs and landings in 2025, and the region is also the largest railroad hub in North America. The Chicago "L" rapid transit, commuter rail, and bus systems make up the second-largest public transit system in the U.S. The Chicago area has one of the highest gross domestic products (GDP) of any urban region in the world, generating nearly $1 trillion in 2026. The Loop is the second-largest central business district in the United States. Chicago's economy is diverse, with no single industry employing more than 14% of the workforce.
Chicago is a major destination for tourism, with nearly 57 million people visiting its cultural institutions, Lake Michigan beaches, restaurants, and other tourist sites in 2025. Chicago's culture has made significant contributions to the visual arts, literature, film, theater, comedy (especially improvisational comedy), food, dance, and music (particularly jazz, blues, soul, hip-hop, gospel, industrial, and electronic dance music, especially house music). Chicago is home to the Chicago Symphony Orchestra and the Lyric Opera of Chicago, while the Art Institute of Chicago has an influential visual arts museum and art school. The Chicago area is home to the University of Chicago, Northwestern University, and the University of Illinois Chicago, among other institutions of higher education. It also hosts the Barack Obama Presidential Center. Professional sports in Chicago include all major professional leagues, including two Major League Baseball teams. The city also hosts the Chicago Marathon, one of the World Marathon Majors.
Etymology and nicknames
The name Chicago is derived from a French rendering of the indigenous Miami–Illinois word šikaakwa, which was a name for a wild relative of onion and garlic known to modern botanists as Allium tricoccum. The first known reference to the site of the city of Chicago as "Checagou" was by Robert de La Salle around 1679 in a memoir. Henri Joutel, in his journal of 1688, noted that the eponymous wild "garlic" grew profusely in the area. According to his diary of late September 1687:
... when we arrived at the said place called "Chicagou" which, according to what we were able to learn of it, has taken this name because of the quantity of garlic which grows in the forests in this region.
The city has had several nicknames throughout its history, such as the Windy City, Chi-Town, Second City, and City of the Big Shoulders.
History
18th century: Potawatomi, Jean Baptiste Point du Sable
In the mid-18th century, the area was inhabited by the Potawatomi, an indigenous tribe who had succeeded the Miami, Sauk and Meskwaki peoples in this region.
The first known permanent settler in Chicago was a trader, Jean Baptiste Point du Sable. Du Sable was of African descent, perhaps born in the French colony of Saint-Domingue (Haiti), and he established the settlement in the 1780s. He is commonly known as the "Founder of Chicago".
In 1795, following the victory of the new United States in the Northwest Indian War, an area that was to be part of Chicago was turned over to the U.S. for a military post by native tribes in accordance with the Treaty of Greenville.
19th century: Growth, major engineering projects
1800–1849: Indian removal, first railroad and canal
In 1803, the U.S. Army constructed Fort Dearborn, which was destroyed during the War of 1812 in the Battle of Fort Dearborn by the Potawatomi before being later rebuilt.
The Odawa, Ojibwe, and Potawatomi tribes ceded additional land to the United States in the 1816 Treaty of St. Louis. The Potawatomi were forcibly removed from their land after the 1833 Treaty of Chicago and sent west of the Mississippi River as part of the federal policy of Indian removal.
On August 12, 1833, the Town of Chicago was organized with a population of about 200. Within seven years it grew to more than 6,000 people. On June 15, 1835, the first public land sales began with Edmund Dick Taylor as Receiver of Public Monies. The City of Chicago was incorporated on Saturday, March 4, 1837, and for several decades was the world's fastest-growing city.
As the site of the Chicago Portage, the city became an important transportation hub between the eastern and western United States. Chicago's first railway, Galena and Chicago Union Railroad, and the Illinois and Michigan Canal opened in 1848. The canal allowed steamboats and sailing ships on the Great Lakes to connect to the Mississippi River.
A flourishing economy brought residents from rural communities and immigrants from abroad. Manufacturing and retail and finance sectors became dominant, influencing the American economy. The Chicago Board of Trade (established 1848) listed the first-ever standardized "exchange-traded" forward contracts, which were called futures contracts.
1850–1874: Raising, water cribs, river reversal, fire
In the 1850s, Chicago gained national political prominence as the home of Senator Stephen Douglas, the champion of the Kansas–Nebraska Act and the "popular sovereignty" approach to the issue of the spread of slavery. These issues also helped propel another Illinoisan, Abraham Lincoln, to the national stage. Lincoln was nominated in Chicago for U.S. president at the 1860 Republican National Convention, which was held in a purpose-built auditorium called the Wigwam. He defeated Douglas in the general election, and this set the stage for the American Civil War.
To accommodate rapid population growth and demand for better sanitation, the city improved its infrastructure. In February 1856, Chicago's Common Council approved Chesbrough's plan to build the United States' first comprehensive sewerage system. The project raised much of central Chicago to a new grade with the use of jackscrews for raising buildings. While elevating Chicago, and at first improving the city's health, the untreated sewage and industrial waste now flowed into the Chicago River, and subsequently into Lake Michigan, polluting the city's primary freshwater source.
The city responded by tunneling two miles (3.2 km) out into Lake Michigan to newly built water cribs. In 1900, the problem of sewage contamination was largely resolved when the city completed a major engineering feat. It reversed the flow of the Chicago River so that the water flowed away from Lake Michigan rather than into it. This project began with the construction and improvement of the Illinois and Michigan Canal, and was completed with the Chicago Sanitary and Ship Canal that connects to the Illinois River, which flows into the Mississippi River.
On October 8, 1871, the Great Chicago Fire destroyed an area about 4 miles (6.4 km) long and 1-mile (1.6 km) wide, a large section of the city at the time. At least 300 people were killed and over 100,000 were left homeless from the fire. However, much of the city, including railroads and stockyards, survived intact, and from the ruins of the previous wooden structures arose more modern constructions of steel and stone. These set a precedent worldwide for construction. During its rebuilding period, Chicago constructed the world's first skyscraper in 1885, using steel-skeleton construction.
1875–1899: Railroads, annexation, health, stature
Labor conflicts followed the industrial boom and the rapid expansion of the labor pool during the Gilded Age, including the Haymarket affair on May 4, 1886, and in 1894 the Pullman Strike. Anarchist and socialist groups played prominent roles in creating very large and highly organized labor actions. Concern for social problems among Chicago's immigrant poor led Jane Addams and Ellen Gates Starr to found Hull House in 1889. Programs that were developed there became a model for the new field of social work.
During the 1870s and 1880s, Chicago attained national stature as the leader in the movement to improve public health. City laws and later, state laws that upgraded standards for the medical profession and fought urban epidemics of cholera, smallpox, and yellow fever were both passed and enforced. These laws became templates for public health reform in other cities and states.
The city established many large, well-landscaped municipal parks, which also included public sanitation facilities. The chief advocate for improving public health in Chicago was John H. Rauch, M.D. Rauch established a plan for Chicago's park system in 1866. He created Lincoln Park by closing a cemetery filled with shallow graves, and in 1867, in response to an outbreak of cholera he helped establish a new Chicago Board of Health. Ten years later, he became the secretary and then the president of the first Illinois State Board of Health, which carried out most of its activities in Chicago.
In the 1800s, Chicago became the nation's railroad hub, and by 1910 over 20 railroads operated passenger service out of six different downtown terminals. In 1883, Chicago's railway managers needed a general time convention, so they developed the standardized system of North American time zones. This system for telling time spread throughout the continent.
The city grew significantly in size and population by incorporating many neighboring townships between 1851 and 1920, with the largest annexation happening in 1889, with five townships joining the city, including the Hyde Park Township, which now comprises most of the South Side of Chicago and the far southeast of Chicago, and the Jefferson Township, which now makes up most of Chicago's Northwest Side. The desire to join the city was driven by municipal services that the city could provide its residents.
In 1893, Chicago hosted the World's Columbian Exposition on former marshland at the present location of Jackson Park. The Exposition drew 27.5 million visitors, and is considered the most influential world's fair in history. The city's municipal device, a Y within a circle, was the result of a contest run by the Chicago Tribune in 1892, in anticipation of the Columbian Exposition. The University of Chicago, formerly at another location, moved to the same South Side location in 1892. The term "midway" for a fair or carnival referred originally to the Midway Plaisance, a strip of park land that still runs through the University of Chicago campus and connects the Washington and Jackson Parks.
20th century: More growth, pluralization, suburbs, Daleys
1900–1924: Industrial growth, prohibition
Chicago's flourishing economy attracted huge numbers of new immigrants from Europe and migrants from the Eastern United States. Of the total population in 1900, more than 77% were either foreign-born or born in the United States of foreign parentage. Germans, Irish, Poles, Swedes, and Czechs made up nearly two-thirds of the foreign-born population (by 1900, whites were 98.1% of the city's population).
During World War I and the 1920s there was a major expansion in industry. The availability of jobs attracted African Americans from the Southern United States. Between 1910 and 1930, the African American population of Chicago increased dramatically, from 44,103 to 233,903. This Great Migration had an immense cultural impact, called the Chicago Black Renaissance, part of the New Negro Movement, in art, literature, and music. Continuing racial tensions and violence in the city, such as the Chicago race riot of 1919, also occurred.
The ratification of the 18th amendment to the Constitution in 1919 made the production and sale (including exportation) of alcoholic beverages illegal in the United States. This ushered in the beginning of what is known as the gangster era, a time that roughly spans from 1919 until 1933 when Prohibition was repealed. The 1920s saw gangsters, including Al Capone, Dion O'Banion, Bugs Moran and Tony Accardo battle law enforcement and each other on the streets of Chicago during the Prohibition era. Chicago was the location of the infamous St. Valentine's Day Massacre in 1929, when Al Capone sent men to gun down members of a rival gang, North Side, led by Bugs Moran, leaving seven rival members dead.
From 1920 to 1921, the city was affected by a series of tenant rent strikes, which led to the formation of the Chicago Tenants Protective association, passage of the Kessenger tenant laws, and of a heat ordinance that legally required flats to be kept above 68 °F during winter months by landlords.
Chicago was the first American city to have a homosexual-rights organization. The organization, formed in 1924, was called the Society for Human Rights. It produced the first American publication for homosexuals, Friendship and Freedom. Police and political pressure caused the organization to disband.
1925–1949: Great Depression, Great Migration
The Great Depression brought unprecedented suffering to Chicago, in no small part due to the city's heavy reliance on heavy industry. Notably, industrial areas on the south side and neighborhoods lining both branches of the Chicago River were devastated; by 1933 over 50% of industrial jobs in the city had been lost, and unemployment rates amongst blacks and Latinos in the city were over 40%. The Republican political machine in Chicago was utterly destroyed by the economic crisis, and every mayor since 1931 has been a Democrat.