The Loop is what locals call the historical center of downtown Chicago. It is the second-largest central business district in the United States, after Midtown Manhattan. Bounded on the west and north by the Chicago River, on the east by Lake Michigan, and on the south by Roosevelt Road, the value of its real-estate shaped an architectural style dominated by high-rises. Notable buildings include the Home Insurance Building, considered the first skyscraper; the Chicago Board of Trade Building, a National Historic Landmark; and the Sears Tower, the tallest in the United States. Some of the historic buildings in this district were instrumental in the development of high-rises. Chicago's rational street numbering system originates in the Loop at the intersection of State Street and Madison Street.

The term "The Loop" has different meanings. As defined by the University of Chicago, the Loop is community area of Chicago number 32. The boundaries as designated by the City of Chicago are the Chicago River to the north and west, Roosevelt Road to the south, and Lake Michigan to the east, though the original boundary is strictly the area circled by the elevated CTA tracks. As the downtown area and its many high-rises expanded out past the community area over the years, "The Loop" has been used more generally to denote the entire downtown as opposed to just the community area. The term even more specifically applies to the section of the community area surrounded by the circuit formed by Chicago's 'L' trains. The circuit runs along Lake Street on the north, Wabash Avenue on the east, Van Buren Street on the south, and Wells Street on the west. The name, however, predates the elevated loop, coming from a streetcar loop in 1882. Currently, most residents probably consider it to be the area bounded by the Chicago River on the north and west sides, Congress Parkway to the South, and Columbus Drive to the east.

This area has a wealth of shopping opportunities, including the Loop Retail Historic District, although it competes with the more upscale Magnificent Mile area to the north, and with suburban shopping malls. It includes Chicago's former Marshall Field's department store location in the Marshall Field and Company Building, now Macy's, a traditional favorite for viewing Christmas window displays; the original Sullivan Center Carson Pirie Scott store location (closed February 21, 2007); and Sears on State.

It is the location of a number of government buildings, including City Hall/County Building, the James R. Thompson Center, the Richard J. Daley Center, and multiple federal buildings. Chicago's Downtown Theatre District is also found within this area, along with numerous restaurants and hotels.

Chicago has a famous skyline which is home to many of the tallest buildings in the world as well as the Chicago Landmark Historic Michigan Boulevard District. Unlike densely packed Midtown Manhattan, Chicago's skyline is spaced out throughout the downtown area, giving it a graceful bridgelike appearance. The Sears Tower, the nation's tallest building, lies at the west end of the Loop in the heart of the city's financial district, along with other buildings, such as 311 South Wacker Drive and the AT&T Corporate Center. Chicago's second tallest building, the Aon Center, is located around the Illinois Center, a complex that stands at the east end of the Loop, east of Michigan Avenue. Two Prudential Plaza is also located here, just to the west of the Aon Center. The city's third tallest building, the John Hancock Center, is located on the Magnificent Mile, north of the Loop in a major shopping area. Water Tower Place, 900 North Michigan, and Park Tower are all located within a block or two of the John Hancock Center, creating an impressive cluster of skyscrapers, unmatched perhaps even in the Loop itself. Although this area is considered part of downtown Chicago, it is not a part of the Loop. It is part of the Near North Side Community Area.

According to the 2000 census, 16,388 people live in the Loop. More recently, 60602 was named by Forbes as the hottest zipcode in the country with upscale buildings such as The Heritage at Millennium Park(130 N. Garland) leading the way for other buildings such at Waterview Tower, The Legacy and Momo. The median sale price for residential real estate was $710,000 in 2005 according to Forbes. The Loop contains a wealth of outdoor sculpture, including works by Pablo Picasso, Joan Miró, Henry Moore, Marc Chagall, Alexander Calder, and Jean Dubuffet. Chicago's cultural heavyweights, such as the Art Institute of Chicago, the Goodman Theatre, the Chicago Theatre, the Lyric Opera at the Civic Opera House building, and the Chicago Symphony Orchestra, are also in this area, as is the historic Palmer House Hilton hotel, found on East Monroe Street.

Chicago's lakefront, which is almost exclusively recreational park area from north to south, features Grant Park in this downtown area. Grant Park is the home of Buckingham Fountain, the Petrillo Bandshell, the Grant Park Symphony (where free concerts can be enjoyed throughout the summer), and Chicago's annual two-week food festival, the Taste of Chicago, where more than 3 million people "pig out". A recent addition to Grant Park is the architecturally forward Millennium Park, which opened in the summer of 2004, featuring a Frank Gehry's Jay Pritzker Pavilion, Jaume Plensa's Crown Fountain and Anish Kapoor's Cloud Gate sculpture and spanning what were formerly open railyards on the city's lakefront.

The Chicago River, which delineates the area, also provides entertainment and recreational opportunities, including the annual dyeing of the river green in honor of St. Patrick's Day. Trips down the Chicago River, including architectural tours, by commercial boat operators are great favorites with both locals and tourists.

The area is served by its own newspaper, the Chicago Journal.

The Loop also hosts America's only city-based dusk-till-dawn cultural celebration, Looptopia. This year, event is scheduled for May 2nd of 2008.

See also: Chicago Loop (a movie by James Benning)