As of the census of 2010, there were 1,921 people, 746 households, and 510 families residing in the city. The population density was. There were 846 housing units at an average density of. The racial makeup of the city was 95.5% White, 0.3% African American, 1.0% Native American, 0.3% Asian, 0.1% Pacific Islander, 0.7% from other races, and 2.1% from two or more races. Hispanic or Latino of any race were 2.8% of the population. There were 746 households of which 36.5% had children under the age of 18 living with them, 46.9% were married couplesliving together, 15.1% had a female householder with no husband present, 6.3% had a male householder with no wife present, and 31.6% were non-families. 28.2% of all households were made up of individuals and 15.2% had someone living alone who was 65 years of age or older. The average household size was 2.52 and the average family size was 3.05. The median age in the city was 39.2 years. 26.7% of residents were under the age of 18; 8.8% were between the ages of 18 and 24; 20.9% were from 25 to 44; 25.4% were from 45 to 64; and 18.1% were 65 years of age or older. The gender makeup of the city was 48.0% male and 52.0% female.
2000 census
As of the census of 2000, there were 1,834 people, 711 households, and 479 families residing in the city. The population density was 699.3 people per square mile. There were 792 housing units at an average density of 302.0 per square mile. The racial makeup of the city was 96.29% White, 0.05% African American, 0.55% Native American, 0.38% Asian, 0.71% from other races, and 2.02% from two or more races. Hispanic or Latino of any race were 1.80% of the population. There were 711 households out of which 35.2% had children under the age of 18 living with them, 50.4% were married couples living together, 13.1% had a female householder with no husband present, and 32.5% were non-families. 29.4% of all households were made up of individuals and 18.6% had someone living alone who was 65 years of age or older. The average household size was 2.50 and the average family size was 3.08. In the city the population was spread out with 28.5% under the age of 18, 8.1% from 18 to 24, 26.6% from 25 to 44, 19.2% from 45 to 64, and 17.7% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 89.5 males. For every 100 females age 18 and over, there were 83.5 males. The median income for a household in the city was $25,093, and the median income for a family was $30,048. Males had a median income of $23,938 versus $18,481 for females. The per capita income for the city was $12,486. About 13.7% of families and 18.1% of the population were below the poverty line, including 20.3% of those under age 18 and 32.1% of those age 65 or over.
Amish community
Outside of Seymour is a large Old Order Amish Community. This community of Swiss Amish was founded in 1968 and consisted of 13 church districts in 2014 and a total Amish population of about 2,250 people. By 2019, the settlement had grown to 16 church districts and approximately 3,270 people, placing it among the 12 largest Amish communities in the world.
Government
The City of Seymour has an alderman/administrator government structure. The current mayor of Seymour is Richard Vinson. The current City Administrator is Hillary Gintz. The chief of Police is Steven Pogue
Education
Public education in Seymour is administered by Seymour R-II School District. Seymour has a public library, the Seymour Community Library.
Arts and culture
The Seymour Merchants Association holds an annual Apple Festival the second weekend of every September. The Ozark Mennonite School holds an Apple Butter Day fundraiser event every 3rd Saturday of every October to support the school.
