Mannsville is a town in Johnston County, Oklahoma, United States. The population was 587 at the 2000 census. Mannsville is located at 34°11′9″N 96°52′49″W (34.185707, -96.880271). According to the United States Census Bureau, the town has a total area of 1.1 square miles (2.8 km2), of which, 1.1 square miles (2.8 km2) of it is land and 0.92% is water. They have a fully staffed Fire Department made up of all volunteers with 3 stations, two in town and one out on in the small community of Greasy Bend.
As of the census of 2000, there were 587 people, 221 households, and 150 families residing in the town. The population density was 543.8 people per square mile (209.9/km²). There were 253 housing units at an average density of 234.4 per square mile (90.4/km²). The racial makeup of the town was 81.77% White, 0.17% African American, 9.88% Native American, 0.34% from other races, and 7.84% from two or more races. Hispanic or Latino of any race were 0.51% of the population.
There were 221 households out of which 33.0% had children under the age of 18 living with them, 51.1% were married couples living together, 13.1% had a female householder with no husband present, and 31.7% were non-families. 25.3% of all households were made up of individuals and 10.0% had someone living alone who was 65 years of age or older. The average household size was 2.66 and the average family size was 3.25.
In the town the population was spread out with 26.6% under the age of 18, 8.3% from 18 to 24, 31.2% from 25 to 44, 21.6% from 45 to 64, and 12.3% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 100.3 males. For every 100 females age 18 and over, there were 95.0 males.
The median income for a household in the town was $24,896, and the median income for a family was $30,982. Males had a median income of $21,838 versus $18,676 for females. The per capita income for the town was $10,683. About 16.0% of families and 20.1% of the population were below the poverty line, including 24.9% of those under age 18 and 17.3% of those age 65 or over.