Basements throughout the Chicago Loop are flooded, forcing the Chicago Board of Trade Building and the Chicago Mercantile Exchange to close.
The Chicago flood occurred on April 13, 1992, when repair work on a bridge spanning the Chicago River damaged the wall of an abandoned and disused utility tunnel beneath the river. The resulting breach flooded basements, facilities and the underground Chicago Pedway throughout the Chicago Loop with an estimated 250 million US gallons (1,000,000 m3) of water.
The remediation lasted for weeks, and cost about $2 billion in 1992 dollars, equivalent to $3.86 billion in 2021. The legal battles lasted for several years, and disagreement over who was at fault persists to this day.
The Loop, one of Chicago's 77 designated community areas, is the central business district of the city and is the main section of Downtown Chicago. Home to Chicago's commercial core, it is the second largest commercial business district in North America and contains the headquarters and regional offices of several global and national businesses, retail establishments, restaurants, hotels, and theaters, as well as many of Chicago's most famous attractions. It is home to Chicago's City Hall, the seat of Cook County, and numerous offices of other levels of government and consulates of foreign nations. In it, at the intersection of State Street and Madison Street, is the origin of Chicago's street grid addresses, established in 1909. Most of Grant Park's 319 acres (1.29 km2) are in the eastern section of the community area. The Loop community area is bounded on the north and west by the Chicago River, on the east by Lake Michigan, and on the south by Roosevelt Road, although the commercial core has greatly expanded into adjacent community areas.
The United States Army erected Fort Dearborn in 1803 in what is now the Loop, the first settlement in the area sponsored by the United States' federal government. When Chicago and Cook County were incorporated in the 1830s the area was selected as the site of their respective seats. Originally mixed use, the character of the area became commercial starting in the 1870s, especially after it was mostly destroyed in the Great Chicago Fire of 1871. At that time some of the world's earliest skyscrapers were constructed in the area, starting a legacy of architecture that continues to this day. In the late 19th century cable car turnarounds and a prominent elevated railway loop encircled the area, giving the Loop its name. Starting in the 1920s many highways were constructed in the Loop, most prominently U.S. Route 66, which opened in 1926 with its eastern terminus in the area.
While dominated by offices and public buildings, its residential population boomed during the latter 20th century and first decades of the 21st; its population has increased the most of Chicago's community areas since 1950.