Marshall County is a county located on the south-central border of Oklahoma. As of the 2020 census, the population was 15,312. Its county seat is Madill. The county was created at statehood in 1907 from the former Pickens County of the Chickasaw Nation. It was named to honor the maiden name of the mother of George Henshaw, a member of the 1906 Oklahoma Constitutional Convention. The county and its cities are part of the Texoma region.
History
The area covered by Marshall County was part of the territory set aside by the U.S. government for resettlement of the Choctaw tribe and the closely related Chickasaw tribe from their lands in the southeastern United States. The Chickasaws began relocating to this area in 1837. The U.S. Army built Fort Washita in 1842 to protect the new arrivals from raids by other tribes. In 1857, the Chickasaw Nation formally separated from the Choctaw Nation. This area became part of Pickens County in the Chickasaw Nation. It is the smallest county in Oklahoma by land area and the third-smallest by total area. The Red River drains the county and forms the county's southern boundary. Completion of the Denison Dam in 1942 created Lake Texoma, which inundated part of Marshall County's land area and formed the current southern boundary and the eastern boundary of the county as well.
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| footnote = U.S. Decennial Census<br />1790-1960 1900-1990<br />1990-2000 2010
2020 census
As of the 2020 census, the county had a population of 15,312. Of the residents, 23.1% were under the age of 18 and 22.2% were 65 years of age or older; the median age was 43.4 years. For every 100 females there were 98.8 males, and for every 100 females age 18 and over there were 96.8 males.
The racial makeup of the county was 66.7% White, 1.1% Black or African American, 9.9% American Indian and Alaska Native, 0.3% Asian, 10.2% from some other race, and 11.8% from two or more races. Hispanic or Latino residents of any race comprised 17.0% of the population.
There were 5,371 households, out of which 27.30% had children under the age of 18 living with them, 58.10% were married couples living together, 8.80% had a female householder with no husband present, and 29.20% were non-families. 26.40% of all households were made up of individuals, and 14.50% had someone living alone who was 65 years of age or older. The average household size was 2.40 and the average family size was 2.87.
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! colspan = 2 | Party
! Number of Voters
! Percentage
|-
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| Democratic
| align = center | 2,460
| align = center | 29.55%
|-
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| Republican
| align = center | 5,175
| align = center | 62.16%
|-
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| Unaffiliated
| align = center | 1,548
| align = center | 18.59%
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! colspan = 2 | Total
! align = center | 8,325
! align = center | 100%
|}
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Economy
During the 19th century, the county's economy was based on agriculture and ranching. Cotton and corn were the most dominant crops. By 1934, oats had become the third-largest crop. After the creation of Lake Texoma, cotton acreage had dropped to about 10 percent of its 1934 level, corn had fallen to less than 2 percent, while peanuts had become the third largest crop. By 2001, wheat had become the largest crop, followed by rye, oats, and peanuts.