Chicago is the third largest city in the United States with more than 2.8 million residents. Adjacent to Lake Michigan, the Chicago metropolitan area (commonly referred to as Chicagoland) has a population of more than 9.7 million people in three U.S. states, Illinois, Wisconsin and Indiana, and was the third largest metropolitan area in 2000. Chicago is partitioned by the city into four main sections: Downtown (which contains the Loop), the North Side, the South Side, and the West Side. In the late 1920s sociologists at the University of Chicago subdivided the city into 77 distinct community areas. The boundaries of these areas are more clearly defined than those of the over 210 neighborhoods throughout the city, allowing for better year-by-year comparisons.
Chicago incorporated as a city in 1837 after being founded in 1833 and soon became the transportation, financial and industrial center of the Midwest. Today the city's attractions bring 44.2 million visitors annually. Chicago became notorious worldwide for its violent gangsters in the 1920s, most notably Al Capone, and for its political corruption in one of the longest tenures of political machinery in the United States. The city has a notable and famous political culture, is a stronghold of the Democratic Party, and has been home to numerous influential politicians, including the first African-American president-elect of the United States, Barack Obama.