Sebeka originally grew around the depot of the K-line branch of the Great Northern Railway, which first came through the area in 1892. The first major industry in the area was logging. The town's first store was the Anderson Pioneer Store. The town was incorporated on March 19, 1898. Its population has gone from 233 in 1900 to a peak of 818 in 1960.
As of the census of 2010, there were 711 people, 321 households, and 182 families residing in the city. The population density was. There were 364 housing units at an average density of. The racial makeup of the city was 97.9% White, 0.4% African American, 0.1% Native American, and 1.5% from two or more races. Hispanic or Latino of any race were 0.8% of the population. There were 321 households of which 27.4% had children under the age of 18 living with them, 40.5% were married couplesliving together, 10.9% had a female householder with no husband present, 5.3% had a male householder with no wife present, and 43.3% were non-families. 38.9% of all households were made up of individuals and 19.3% had someone living alone who was 65 years of age or older. The average household size was 2.21 and the average family size was 2.96. The median age in the city was 38.3 years. 26.2% of residents were under the age of 18; 6.7% were between the ages of 18 and 24; 23.3% were from 25 to 44; 23.1% were from 45 to 64; and 20.7% were 65 years of age or older. The gender makeup of the city was 47.8% male and 52.2% female.
2000 census
As of the census of 2000, there were 710 people, 332 households, and 188 families residing in the city. The population density was 289.1 people per square mile. There were 378 housing units at an average density of 153.9 per square mile. The racial makeup of the city was 99.01% White, 0.14% African American, 0.28% Native American, and 0.56% from two or more races. Hispanic or Latino of any race were 2.54% of the population. 30.1% were of Finnish, 28.2% German, 9.2% Norwegian and 7.6% American ancestry. There were 332 households out of which 26.2% had children under the age of 18 living with them, 45.5% were married couples living together, 8.4% had a female householder with no husband present, and 43.1% were non-families. 40.7% of all households were made up of individuals and 25.0% had someone living alone who was 65 years of age or older. The average household size was 2.13 and the average family size was 2.86. In the city, the population was spread out with 23.9% under the age of 18, 8.3% from 18 to 24, 23.0% from 25 to 44, 19.9% from 45 to 64, and 24.9% who were 65 years of age or older. The median age was 41 years. For every 100 females, there were 88.3 males. For every 100 females age 18 and over, there were 82.4 males. The median income for a household in the city was $23,693, and the median income for a family was $36,429. Males had a median income of $27,115 versus $19,531 for females. The per capita income for the city was $14,933. About 11.7% of families and 17.8% of the population were below the poverty line, including 20.6% of those under age 18 and 20.2% of those age 65 or over.
