Madill is a city in Marshall County, Oklahoma, United States. The city was founded in 1901 and is named for George Alexander Madill, an attorney for the St. Louis-San Francisco Railway, popularly known as the Frisco. The population was 3,410 at the 2000 census. It is the county seat of Marshall County.
According to the United States Census Bureau, the city has a total area of 2.9 square miles (7.6 km²), of which, 2.9 square miles (7.5 km²) of it is land and 0.04 square miles (0.1 km²) of it (1.37%) is water.
Madill is about 10 miles north of Lake Texoma.
There were 1,284 households out of which 32.6% had children under the age of 18 living with them, 47.7% were married couples living together, 12.5% had a female householder with no husband present, and 35.3% were non-families. 32.2% of all households were made up of individuals and 19.4% had someone living alone who was 65 years of age or older. The average household size was 2.47 and the average family size was 3.12.
In the city the population was spread out with 26.8% under the age of 18, 9.7% from 18 to 24, 25.3% from 25 to 44, 18.7% from 45 to 64, and 19.6% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 90.1 males. For every 100 females age 18 and over, there were 86.3 males.
The median income for a household in the city was $22,457, and the median income for a family was $26,892. Males had a median income of $22,420 versus $18,203 for females. The per capita income for the city was $12,614. About 19.2% of families and 26.1% of the population were below the poverty line, including 36.2% of those under age 18 and 19.7% of those age 65 or over.