|Sioux County, North Dakota|
Location within the U.S. state of North Dakota
North Dakota's location within the U.S.
|Founded||September 12, 1914|
|Named for||Sioux people|
|Largest community||Cannon Ball|
|• Total||1,128 sq mi (2,922 km2)|
|• Land||1,094 sq mi (2,833 km2)|
|• Water||34 sq mi (88 km2), 3.0%|
|• ( 2017)||4,376|
|• Density||3.8/sq mi (1.5/km2)|
Sioux County is a county located along the southern border of the U.S. state of North Dakota. As of the 2010 census, the population was 4,153.  Its eastern border is the Missouri River and its county seat is Fort Yates.  The county was created by proclamation of Governor Louis B. Hanna on September 3, 1914 and named after the Native American Lakota, whose historic territory included this area and much more. The county government was first organized on September 12, 1914.  
The county lies entirely within the Standing Rock Indian Reservation, forming the northernmost 30 percent of the reservation. (The balance of the reservation is in South Dakota). It is the only county in North Dakota that is entirely within an Indian reservation. Sioux County is included in the Bismarck, ND Metropolitan Statistical Area.
According to the U.S. Census Bureau, the county has a total area of 1,128 square miles (2,920 km2), of which 1,094 square miles (2,830 km2) is land and 34 square miles (88 km2) (3.0%) is water.  The Missouri River and Lake Oahe form the eastern border of the county.
- Morton County (north)
- Emmons County (east)
- Corson County, South Dakota (south)
- Adams County (west)
- Grant County (northwest)
|U.S. Decennial Census
1790-1960  1900-1990 
1990-2000  2010-2017 
As of the census of 2000, there were 4,044 people, 1,095 households, and 871 families residing in the county. The population density was 4 people per square mile (1/km²). There were 1,216 housing units at an average density of 1 per square mile (0/km²). The racial makeup of the county was 84.59% Native American, 14.34% White, 0.02% Black or African American, 0.02% Asian, 0.05% Pacific Islander, 0.07% from other races, and 0.89% from two or more races. 1.61% of the population were Hispanic or Latino of any race. 11.5% were of German ancestry.
There were 1,095 households out of which 48.90% had children under the age of 18 living with them, 39.10% were married couples living together, 29.10% had a female householder with no husband present, and 20.40% were non-families. 16.60% of all households were made up of individuals and 4.40% had someone living alone who was 65 years of age or older. The average household size was 3.63 and the average family size was 3.98.
In the county, the population was spread out with 40.30% under the age of 18, 11.10% from 18 to 24, 26.90% from 25 to 44, 16.20% from 45 to 64, and 5.60% who were 65 years of age or older. The median age was 24 years. For every 100 females there were 104.20 males. For every 100 females age 18 and over, there were 99.70 males.
The median income for a household in the county was $22,483, and the median income for a family was $24,000. Males had a median income of $22,039 versus $19,458 for females. The per capita income for the county was $7,731. About 33.60% of families and 39.20% of the population were below the poverty line, including 44.40% of those under age 18 and 25.80% of those age 65 or over. The county's per-capita income makes it one of the poorest counties in the United States.
As of the 2010 United States Census, there were 4,153 people, 1,158 households, and 900 families residing in the county.  The population density was 3.8 inhabitants per square mile (1.5/km2). There were 1,311 housing units at an average density of 1.2 per square mile (0.46/km2).  The racial makeup of the county was 84.1% American Indian, 12.6% white, 0.2% black or African American, 0.1% Asian, 0.1% from other races, and 2.9% from two or more races. Those of Hispanic or Latino origin made up 2.0% of the population.  In terms of ancestry, 13.5% were German, and 0.3% were American. 
Of the 1,158 households, 54.1% had children under the age of 18 living with them, 32.5% were married couples living together, 31.6% had a female householder with no husband present, 22.3% were non-families, and 17.4% of all households were made up of individuals. The average household size was 3.55 and the average family size was 3.89. The median age was 26.3 years. 
The median income for a household in the county was $30,990 and the median income for a family was $31,098. Males had a median income of $31,894 versus $26,619 for females. The per capita income for the county was $13,542. About 39.0% of families and 47.2% of the population were below the poverty line, including 58.4% of those under age 18 and 36.1% of those age 65 or over. 
With its population being mostly Native American, Sioux County is one of the most consistently Democratic counties in North Dakota, having last backed a Republican presidential candidate in 1980. In 2016, Hillary Clinton won the votes in Sioux County, one of only two counties she won in the state.
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