Plankinton sprang up with the arrival of the Chicago, Milwaukee, St. Paul and Pacific Railroad to the area in 1880. The town was named for Milwaukee-based meatpacker and railroad official John Plankinton. The voters approved the incorporation of Plankinton as a village in an election on September 7, 1882. The first officials were elected on September 22, 1882. The first village trustees were C. Thompson, C.C. Irons, T.C. Granger, W.H. Ferguson. Plankinton was home to an annual wheat palace, which became a successful regional attraction and inspired the Corn Palace in nearby Mitchell, South Dakota. The first Grain Palace in South Dakota opened in Plankinton on September 29, 1891. The last one closed in October 1892.
As of the census of 2010, there were 707 people, 294 households, and 191 families residing in the city. The population density was. There were 341 housing units at an average density of. The racial makeup of the city was 92.8% White, 0.7% African American, 0.4% Native American, 5.8% from other races, and 0.3% from two or more races. Hispanic or Latino of any race were 10.2% of the population. There were 294 households of which 30.6% had children under the age of 18 living with them, 50.7% were married couplesliving together, 10.2% had a female householder with no husband present, 4.1% had a male householder with no wife present, and 35.0% were non-families. 29.9% of all households were made up of individuals and 13.3% had someone living alone who was 65 years of age or older. The average household size was 2.40 and the average family size was 2.99. The median age in the city was 38.6 years. 26.2% of residents were under the age of 18; 4.7% were between the ages of 18 and 24; 26.3% were from 25 to 44; 25.5% were from 45 to 64; and 17.3% were 65 years of age or older. The gender makeup of the city was 49.6% male and 50.4% female.
2000 census
As of the census of 2000, there were 601 people, 265 households, and 170 families residing in the city. The population density was 920.6 people per square mile. There were 298 housing units at an average density of 456.5 per square mile. The racial makeup of the city was 94.51% White, 0.17% Native American, 0.17% Asian, 3.99% from other races, and 1.16% from two or more races. Hispanic or Latino of any race were 5.99% of the population. There were 265 households out of which 25.3% had children under the age of 18 living with them, 53.2% were married couples living together, 7.5% had a female householder with no husband present, and 35.5% were non-families. 34.3% of all households were made up of individuals and 20.4% had someone living alone who was 65 years of age or older. The average household size was 2.27 and the average family size was 2.89. In the city, the population was spread out with 22.1% under the age of 18, 8.0% from 18 to 24, 23.1% from 25 to 44, 26.0% from 45 to 64, and 20.8% who were 65 years of age or older. The median age was 42 years. For every 100 females, there were 95.8 males. For every 100 females age 18 and over, there were 91.0 males. The median income for a household in the city was $32,019, and the median income for a family was $40,809. Males had a median income of $26,645 versus $19,531 for females. The per capita income for the city was $15,611. About 3.5% of families and 6.2% of the population were below the poverty line, including 5.1% of those under age 18 and 6.8% of those age 65 or over.
