Sioux City ( ) is a city in Woodbury and Plymouth counties in the U.S. state of Iowa. The population was 85,797 at the 2020 census, and was estimated at 86,875 in 2024,
thumb|1859 map of route from Sioux City, Iowa, through Nebraska, to gold fields of Wyoming, partially following old Mormon trails
Sioux City was laid out in the winter of 1854–1855. It became a major transportation hub to the western Plains, including Mormons heading to Salt Lake City and speculators heading to Wyoming goldfields.
In 1891, the Sioux City Elevated Railway was opened and became the third steam-powered elevated rapid transit system in the world, and later the first electric-powered elevated railway in the world after conversion in 1892. However, the system fell into bankruptcy and closed within a decade.
The city gained the nickname "Little Chicago" during the Prohibition era due to its reputation for being a purveyor of alcoholic beverages.
On July 19, 1989, United Airlines Flight 232 crash-landed at Sioux Gateway Airport. 112 people on board the aircraft were killed, but 184 survived the crash and ensuing fire due to outstandingly quick performances by fire and emergency local teams.
According to a 2015 University of Iowa study for the Iowa Initiative for Sustainable Communities, blight and disinvestment are serious problems in the downtown core as investment has shifted to suburbs.
Geography
Sioux City borders two states, South Dakota to the northwest and Nebraska to the southwest.
According to the United States Census Bureau, the city has a total area of , of which is land and (1.93%) is water. The normal monthly mean temperature ranges from in January to in July. On average, there are 25 days that reach or higher, 52 days that do not climb above freezing, and 17 days with a low of or below annually. The average window for freezing temperatures is October 1 through April 26, allowing a growing season of 157 days. Extreme temperatures officially range from on January 12, 1912 up to on July 4, 1936 and July 17, 1936, as well as July 11, 1939; the record cold daily maximum is on February 8, 1899, while, conversely, the record warm daily minimum is on August 18, 1936. On 14 May 2013, the high temperature reached , setting a new all-time May record high, along with a rise from the morning of the 12th, just two weeks after the city’s first measurable snowfall ( on May 1) recorded in the month of May.
Precipitation is greatest in May and June and averages annually but has ranged from in 1976 to in 1903. Snowfall averages per season, and has historically ranged from in 1895–1896 to in 1961–1962; the average window for measurable (≥) snowfall is November 8 through April 7, although snow in October occurs several times per decade.