According to the 2010 census, the county has a total area of 624.77 square miles (1,618.1 km2), of which 626.42 square miles (1,622.4 km2) (or 99.96%) is land and 0.24 square miles (0.62 km2) (or 0.04%) is water.
There were 20,140 households out of which 33.10% had children under the age of 18 living with them, 60.50% were married couples living together, 8.80% had a female householder with no husband present, and 26.80% were non-families. 22.70% of all households were made up of individuals and 9.70% had someone living alone who was 65 years of age or older. The average household size was 2.57 and the average family size was 3.00.
In the county the population was spread out with 26.30% under the age of 18, 8.70% from 18 to 24, 27.10% from 25 to 44, 23.80% from 45 to 64, and 14.00% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 95.60 males. For every 100 females age 18 and over, there were 92.30 males.
The median income for a household in the county was $35,041, and the median income for a family was $40,616. Males had a median income of $30,057 versus $21,380 for females. The per capita income for the county was $17,502. About 8.10% of families and 11.60% of the population were below the poverty line, including 14.20% of those under age 18 and 9.50% of those age 65 or over.
District 131 – Bill Lant (R-Joplin) Consists of the cities of Diamond, Fairview, and Granby, and the villages of Loma Linda, Newtonia, Redings Mill, Ritchey, Saginaw, Shoal Creek Estates, Silver Creek, Stark City, Stella, and Wentworth.
Missouri House of Representatives - District 131 - Newton County (2010)