During its first 100 years as a city, Chicago grew at a rate that ranked among the fastest growing in the world. When founded in 1833, less than 200 people had settled on what was then the American frontier. By the time of its first census, seven years later, the population had reached over 4000. Within the span of forty years, the city's population grew from slightly under 30,000 in 1850 to over 1 million by 1890. By the close of the 19th century, Chicago was the fifth largest city in the world, and the largest of the cities that did not exist at the dawn of the century. Within fifty years of the Great Chicago Fire of 1871, the population had tripled to over 3 million, and reached its highest ever-recorded population of 3.6 million for the 1950 census.
As of the 2010 census, there were 2,695,598 people with 1,045,560 households residing within Chicago. More than half the population of the state of Illinois lives in the Chicago metropolitan area. Chicago is also one of the nation's most densely populated major cities. The racial composition of the city was:
- 45.0% White (31.7% non-Hispanic whites)
- 32.9% Black or African American
- 28.9% Hispanics or Latinos (of any race)
- 13.4% from some other race
- 5.5% Asian
- 2.7% from two or more races
- 0.5% American Indian
Based on Census data from 2000, the median income for a household in the city was $38,625, and the median income for a family was $42,724. Males had a median income of $35,907 versus $30,536 for females. About 16.6% of families and 19.6% of the population lived below the poverty line.
According to the 2008 American Community Survey 1-Year Estimates for Total Ancestry Reported, for the city of Chicago, the majority of residents, or 64% of 2,986,974 people, reported their ancestry as "other groups". Of the 36% of residents that reported their ancestries in groups that were measured by the U.S. Census Bureau, the largest groups, based on the total population, were: Irish (6.6%); German (6.5%); Polish (5.8%); Italian (3.5%); Assyrian (3.5%); English (2.0%); Sub-Saharan African (1.2%); American(1.1%);Filipino (1.0%); Russian (0.97%); Swedish (0.91%); French (except Basque) (0.9%); Arab (0.7%); Greek (0.6%); Dutch (0.5%); Norwegian (0.5%); Scottish (0.5%); European(0.5%); West Indian (0.5%); Lithuanian (0.4%); Ukrainian (0.38%); Czech (0.4%); Hungarian (0.3%); Scotch-Irish (0.2%); Welsh (0.2%); Danish (0.2%); French Canadian (0.2%);Slovak (0.2%); British (0.1%); Swiss (0.1%); and Portuguese (0.1%). The city also has the largest Assyrian population in the world, numbering between 80,000–120,000, and it is the location of the seat of the head of the Assyrian Church of the East, Mar Dinkha IV.