The city was named as the county seat in 1873, and its position survived a challenge by Superior in 1889. Nelson's population reached a high of 1,000 in 1900, but has since declined gradually.
As of the census of 2010, there were 488 people, 243 households, and 143 families residing in the city. The population density was. There were 300 housing units at an average density of. The racial makeup of the city was 97.7% White, 0.2% from other races, and 2.0% from two or more races. Hispanic or Latino of any race were 1.6% of the population. There were 243 households of which 21.0% had children under the age of 18 living with them, 46.5% were married couplesliving together, 8.2% had a female householder with no husband present, 4.1% had a male householder with no wife present, and 41.2% were non-families. 37.4% of all households were made up of individuals and 20.1% had someone living alone who was 65 years of age or older. The average household size was 2.01 and the average family size was 2.59. The median age in the city was 50.3 years. 19.9% of residents were under the age of 18; 4.4% were between the ages of 18 and 24; 18.4% were from 25 to 44; 29% were from 45 to 64; and 28.3% were 65 years of age or older. The gender makeup of the city was 49.0% male and 51.0% female.
2000 census
As of the census of 2000, there were 587 people, 271 households, and 150 families residing in the city. The population density was 724.8 people per square mile. There were 312 housing units at an average density of 385.2 per square mile. The racial makeup of the city was 99.49% White and 0.51% from two or more races. Hispanic or Latino of any race were 1.19% of the population. There were 271 households out of which 22.9% had children under the age of 18 living with them, 46.1% were married couples living together, 7.0% had a female householder with no husband present, and 44.6% were non-families. 41.7% of all households were made up of individuals and 25.5% had someone living alone who was 65 years of age or older. The average household size was 2.01 and the average family size was 2.73. In the city, the population was spread out with 20.3% under the age of 18, 3.9% from 18 to 24, 21.0% from 25 to 44, 23.7% from 45 to 64, and 31.2% who were 65 years of age or older. The median age was 50 years. For every 100 females, there were 80.6 males. For every 100 females age 18 and over, there were 75.9 males. As of 2000 the median income for a household in the city was $32,500, and the median income for a family was $40,469. Males had a median income of $25,417 versus $22,500 for females. The per capita income for the city was $17,221. About 5.2% of families and 9.4% of the population were below the poverty line, including 14.8% of those under age 18 and 8.5% of those age 65 or over.
