The latest estimate for the population of Chicago, Illinois comes from the US Census Bureau. They confirmed that, in July 2011, there were 2,707,120 people living in the city of Chicago. The population has been estimated to be approximately 2,679,080, with slow growth and declines attributed to violence, tax increases and issues with schools.
This estimate is based on extrapolating the 2010 census data, which reported that the city was home to 2,695,598 people. The 2010 census showed a dramatic drop of almost 7% over the previous ten years, so if the Census Bureau's 2011 figures are correct, they would appear to show Chicago tentatively entering a new period of growth.
The 2016 estimated population of 2.7 million makes Chicago the third largest city in the United States, behind New York City (8.55 million) and Los Angeles (3.97 million). Chicago is by far the largest city in Illinois, with the next largest city, Aurora, being under 200,000 people.
Population of the Chicago Metropolitan Area
Today, Chicago the city makes up only just over a quarter of the wider Chicago-Joliet-Naperville Metropolitan Area's population. According to data from the 2010 census, the CJN Metro Area is home to an impressive 9,504,753 people. In 2016, this number is estimated to be around 9,554,598. Like the city of Chicago, the CJN Metro Area is also the third largest in the US, behind New York-Northern New Jersey-Long Island (20.18 million) and the Los Angeles-Long Beach-Santa Ana (13.34 million) metro areas.
As the population of Chicago itself has gradually fallen, the population of its wider metro area has grown, representing both natural growth in those areas and a gradual move of the city's workforce into its suburbs. Like Chicago itself, the northern suburbs are relatively more affluent than its southern suburbs.
The city's white population is found primarily in the Northern part of the city, and its black community in the Southern part of the city (as can be seen from this map, in which red dots represent Whites, blue dots represent Blacks and orange dots represent Hispanics.) The geographical distribution of race in Chicago is mostly a result of Chicago's historically racist housing allocation policy, which forced its black population into the cheaper Chicago South Side.
Looking back into historical data also shows some interesting trends – non-Hispanic whites made up 59% of the residents of Chicago in 1970, falling to just 31.7% in 2010 – which indicates that many of the people leaving the city over the past few decades for the suburbs have been from among its relatively more affluent white population.
Chicago Census 2010 - further reading
The best source for official data about Chicago from the 2010 census is, of course, the official census website. The census.gov Chicago quick facts page contains not only high-level data on Chicago's population, but also more detailed statistics on the average income in Chicago, the city's age distribution, its businesses, and other important facts.
You can also find some interesting data, including some useful Chicago population maps at the University of Chicago library website and a great news portal covering the 2010 census as it applied to the Windy City at the Chicago Tribune newspaper.
Finally, just as a word of caution to indicate that published statistics aren't always the final word, this article in the Chicago Tribune reports that Mayor Rahm Emanuel is challenging the results of the 2010 census. He believes that the census undercounted the city's population by around 200,000 people. Why is this so important to him? Because millions of dollars of federal subsidies, which are allocated based on relative population, are at stake.