Mangum is a city in and county seat of Greer County, Oklahoma, United States. The population was 3,010 at the 2010 census. It was originally part of Old Greer County in the Texas panhandle. The community was named for A. S. Mangum, who owned the land on which the town was founded in 1882. It became part of Oklahoma Territory in 1896, and thus part of the state of Oklahoma on November 16, 1907.
According to the United States Census Bureau, the city has a total area of 1.8 square miles (4.7 km), all land.
As of the census of 2000, there were 2,924 people, 1,236 households, and 765 families residing in the city. The population density was 1,673.2 people per square mile (645.1/km²). There were 1,553 housing units at an average density of 888.7 per square mile (342.6/km²). The racial makeup of the city was 84.44% White, 6.74% African American, 1.37% Native American, 0.10% Asian, 4.51% from other races, and 2.84% from two or more races. Hispanic or Latino of any race were 8.41% of the population.
There were 1,236 households out of which 25.9% had children under the age of 18 living with them, 47.0% were married couples living together, 11.2% had a female householder with no husband present, and 38.1% were non-families. 36.0% of all households were made up of individuals and 23.2% had someone living alone who was 65 years of age or older. The average household size was 2.25 and the average family size was 2.92.
In the city, the population was spread out with 23.8% under the age of 18, 8.1% from 18 to 24, 21.7% from 25 to 44, 22.9% from 45 to 64, and 23.4% who were 65 years of age or older. The median age was 42 years. For every 100 females, there were 89.1 males. For every 100 females age 18 and over, there were 85.1 males.
The median income for a household in the city was $25,064, and the median income for a family was $30,547. Males had a median income of $26,250 versus $16,198 for females. The per capita income for the city was $13,392. About 20.2% of families and 24.2% of the population were below the poverty line, including 33.3% of those under age 18 and 19.5% of those age 65 or over.