Knox County is a county located in the northeast portion of the U.S. state of Missouri. As of the 2020 census,^[1] its population was 3,744,^[2] making it the third-least populous county in Missouri. Its county seat is Edina.^[3] The county was organized February 14, 1845 and named for U.S. Secretary of War General Henry Knox.^[4]

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Knox County
County
Knox County Courthouse in Edina
Location within the U.S. state of Missouri
Missouri's location within the U.S.
Coordinates: 40°07′N 92°09′W
Country	United States
State	Missouri
Founded	February 14, 1845
Named for	Henry Knox
Seat	Edina
Largest city	Edina
Area
• Total	507 sq mi (1,310 km2)
• Land	504 sq mi (1,310 km2)
• Water	2.8 sq mi (7 km2)  0.6%
Population  (2020)
• Total	3,744
• Density	7.4/sq mi (2.9/km2)
Time zone	UTC−6 (Central)
• Summer (DST)	UTC−5 (CDT)
Congressional district	6th
Website	www.knoxcountymo.org

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A battle was fought during the American Civil War at Newark, involving Joseph C. Porter on August 1, 1862.^[5]

According to the U.S. Census Bureau, the county has a total area of 507 square miles (1,310 km²), of which 504 square miles (1,310 km²) is land and 2.8 square miles (7.3 km²) (0.6%) is water.^[6]

As of the census^[11] of 2010, there were 4,131 people in the county, organized into 1,791 households and 1,217 families. The population density was 9 people per square mile (3.5 people/km²). There were 2,317 housing units at an average density of 5 units per square mile (1.9/km²). The racial makeup of the county was 98.51% White, 0.09% Black or African American, 0.09% Asian, 0.02% Native American, 0.16% from other races, and 1.12% from two or more races. Approximately 0.60% of the population were Hispanic or Latino of any race.

There were 1,791 households, out of which 27.90% had children under the age of 18 living with them, 57.50% were married couples living together, 6.90% had a female householder with no husband present, and 32.00% were non-families. 29.30% of all households were made up of individuals, and 16.00% had someone living alone who was 65 years of age or older. The average household size was 2.38 and the average family size was 2.93.

24.90% of the county's population was under the age of 18, 6.20% from 18 to 24, 23.70% from 25 to 44, 23.90% from 45 to 64, and 21.20% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 92.9 males. For every 100 females age 18 and over, there were 91.6 males.

The median income for a household in the county was $27,124, and the median income for a family was $31,741. Males had a median income of $22,636 versus $18,902 for females. The per capita income for the county was $13,075. 18.00% of the population and 12.90% of families were below the poverty line. Out of the total population, 24.10% of those under the age of 18 and 16.50% of those 65 and older were living below the poverty line.

The TFR for Knox County in 2004 was relatively high at 2.64, despite the population being 98% white.^[12]

• Terry Joyce, collegiate football All-American and professional football player.
• George Turner, U.S. Senator

• List of counties in Missouri
• National Register of Historic Places listings in Knox County, Missouri