Iowa is in the tallgrass prairie of the North American Great Plains, historically inhabited by speakers of Siouan languages. The area of Sioux City was inhabited by Yankton Sioux when it was first reached by Spanish and French furtrappers in the 18th century. The first documented US citizens to record their travels through this area were Meriwether Lewis and William Clark during the summer of 1804. Sergeant Charles Floyd, a member of the Lewis and Clark Expedition, died here on August 20, 1804, the only death during the two and a half-year expedition.

Sioux City was laid out in the winter of 1854-55. It became a major Entrepôt 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, killing 111 people, but 184 survived the crash and ensuing fire due to outstandingly quick performances by fire and emergency local teams that earned them several National Congress Medals, given by President George H. W. Bush in 1990.^{[citation needed]}

Sioux City is located at 42°29′53″N 96°23′45″W / 42.49806°N 96.39583°W / 42.49806; -96.39583 (42.497957, −96.395705). Sioux City lies at an altitude of 1,135 feet (345.9 m) above sea level. Sioux City borders two states, South Dakota to the west-northwest and Nebraska to the west. According to the United States Census Bureau, the city has a total area of 58.49 square miles (151.49 km²), of which 57.35 square miles (148.54 km²) is land and 1.14 square miles (2.95 km²) is water.

As is typical of Iowa, Sioux City has a humid continental climate, with very warm, humid summers, cold, dry winters, and wide temperature extremes; it is part of USDA Hardiness zone 5a. The normal monthly mean temperature ranges from 20.4 °F (−6.4 °C) in January to 74.3 °F (23.5 °C) in July. On average, there are 25 days that reach 90 °F (32 °C) or higher, 52 days that do not climb above freezing, and 17 days with a low of 0 °F (−18 °C) or below annually. The average window for freezing temperatures is October 1 thru April 26, allowing a growing season of 157 days. Extreme temperatures officially range from −35 °F (−37 °C) on January 12, 1912 up to 111 °F (44 °C) on July 4 and 17, 1936 as well as July 11, 1939; the record cold daily maximum is −22 °F (−30 °C) on February 8, 1899, while, conversely, the record warm daily minimum is 86 °F (30 °C) on August 18, 1936.

Precipitation is greatest in May and June and averages 27.7 in (700 mm) annually, but has ranged from 14.33 in (364 mm) in 1976 to 41.10 in (1,044 mm) in 1903. Snowfall averages 34.8 in (88 cm) per season, and has historically ranged from 6.9 in (18 cm) in 1895–96 to 65.9 in (167 cm) in 1961–62; the average window for measurable (≥0.1 in or 0.25 cm) snowfall is November 8 thru April 7, although snow in October occurs several times per decade. On May 14, 2013, the high temperature reached 106 °F (41 °C), setting a new all-time May record high, along with a 77 °F (43 °C) rise from the morning of the 12th.

As of the census of 2010, there were 82,684 people, 31,571 households, and 20,144 families residing in the city. The population density was 1,441.7 inhabitants per square mile (556.6/km²). There were 33,425 housing units at an average density of 582.8 per square mile (225.0/km²). The racial makeup of the city was 80.6% White, 2.9% African American, 2.6% Native American, 2.7% Asian, 0.1% Pacific Islander, 7.4% from other races, and 3.7% from two or more races. Hispanic or Latino of any race were 16.4% of the population.

There were 31,571 households, of which 34.3% had children under the age of 18 living with them, 44.2% were married couples living together, 13.8% had a female householder with no husband present, 5.9% had a male householder with no wife present, and 36.2% were non-families. 29.4% of all households were made up of individuals, and 11.1% had someone living alone who was 65 years of age or older. The average household size was 2.54 and the average family size was 3.14.

The median age in the city was 33.7 years. 26.6% of residents were under the age of 18; 11.4% were between the ages of 18 and 24; 25.6% were from 25 to 44; 24% were from 45 to 64, and 12.4% were 65 years of age or older. The gender makeup of the city was 49.2% male and 50.8% female.

As of the census of 2000, there were 85,013 people, 32,054 households, and 21,091 families residing in the city. The population density was 1,551.3 people per square mile (599.0/km²). There were 33,816 housing units at an average density of 617.1 per square mile (238.3/km²). The racial makeup of the city was 85.23% White, 2.41% African American, 1.95% Native American, 2.82% Asian, 0.04% Pacific Islander, 5.27% from other races, and 2.28% from two or more races. Hispanic or Latino of any race were 10.89% of the population.

There were 32,054 households, of which 33.4% had children under the age of 18 living with them, 49.1% were married couples living together, 12.2% had a female householder with no husband present, and 34.2% were non-families. 27.7% of all households were made up of individuals, and 11.3% had someone living alone who was 65 years of age or older. The average household size was 2.57 and the average family size was 3.14.

Age spread: 27.1% under the age of 18, 11.0% from 18 to 24, 28.5% from 25 to 44, 20.2% from 45 to 64, and 13.3% who were 65 years of age or older. The median age was 33 years. For every 100 females, there were 95.4 males. For every 100 females age 18 and over, there were 92.2 males.

The median income for a household in the city was $37,429, and the median income for a family was $45,751. Males had a median income of $31,385 versus $22,470 for females. The per capita income for the city was $18,666. About 7.9% of families and 11.2% of the population were below the poverty line, including 15.0% of those under age 18 and 7.8% of those age 65 or over. This compares with a median household income for the state of Iowa of $54,736 and an Iowa median family income of $69,382. (current data from State of Iowa, see also List of U.S. states by income for historical data).

As of the 2010 census, the Sioux City Metropolitan Area had 168,825 residents in five counties; the population was estimated at 169,405 in 2018. As defined by the Office of Management and Budget, the counties comprising the metropolitan area are (in descending order of population):