Walnut was originally called Glenwood, and under the latter name laid out in 1871. In 1874, it was renamed Walnut after the Little Walnut Creek, on which it is located. The first post office at Walnut was established in April, 1873. Prior to April, 1877, the post office's name was officially called Walnut Station.
Geography
Walnut is located at . According to the United States Census Bureau, the city has a total area of, of which, is land and is water.
As of the census of 2010, there were 220 people, 84 households, and 57 families living in the city. The population density was. There were 108 housing units at an average density of. The racial makeup of the city was 96.8% White, 1.8% Native American, 0.5% from other races, and 0.9% from two or more races. Hispanic or Latino of any race were 3.6% of the population. There were 84 households of which 40.5% had children under the age of 18 living with them, 53.6% were married couplesliving together, 9.5% had a female householder with no husband present, 4.8% had a male householder with no wife present, and 32.1% were non-families. 29.8% of all households were made up of individuals and 7.2% had someone living alone who was 65 years of age or older. The average household size was 2.62 and the average family size was 3.26. The median age in the city was 30.8 years. 34.1% of residents were under the age of 18; 5.5% were between the ages of 18 and 24; 30% were from 25 to 44; 21.4% were from 45 to 64; and 9.1% were 65 years of age or older. The gender makeup of the city was 49.1% male and 50.9% female.
2000 census
As of the census of 2000, there were 221 people, 91 households, and 55 families living in the city. The population density was 223.1 people per square mile. There were 116 housing units at an average density of 117.1 per square mile. The racial makeup of the city was 98.19% White, 0.90% Asian, and 0.90% from two or more races. Hispanic or Latino of any race were 0.45% of the population. There were 91 households out of which 31.9% had children under the age of 18 living with them, 53.8% were married couples living together, 3.3% had a female householder with no husband present, and 38.5% were non-families. 36.3% of all households were made up of individuals and 16.5% had someone living alone who was 65 years of age or older. The average household size was 2.43 and the average family size was 3.21. In the city, the population was spread out with 29.4% under the age of 18, 9.0% from 18 to 24, 24.9% from 25 to 44, 23.5% from 45 to 64, and 13.1% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 106.5 males. For every 100 females age 18 and over, there were 102.6 males. The median income for a household in the city was $24,000, and the median income for a family was $37,083. Males had a median income of $21,250 versus $23,750 for females. The per capita income for the city was $12,920. About 3.3% of families and 10.6% of the population were below the poverty line, including none of those under the age of eighteen and 25.0% of those sixty five or over.
Economy
The economy of Walnut is mostly agricultural based.
