The geographical center of North America is in Pierce County, about 6 miles (10 km) west of Balta. Rugby has a monument for the center at the intersection of US 2 and ND 3.
As of the census of 2000, there were 4,675 people, 1,964 households, and 1,276 families residing in the county. The population density was 5 people per square mile (2/km²). There were 2,269 housing units at an average density of 2 per square mile (1/km²). The racial makeup of the county was 98.50% White, 0.11% Black or African American, 0.68% Native American, 0.26% Asian, 0.04% from other races, and 0.41% from two or more races. 0.60% of the population were Hispanic or Latino of any race. 47.7% were of German and 32.7% Norwegian ancestry according to Census 2000.
There were 1,964 households out of which 28.20% had children under the age of 18 living with them, 56.40% were married couples living together, 6.30% had a female householder with no husband present, and 35.00% were non-families. 32.00% of all households were made up of individuals and 17.10% had someone living alone who was 65 years of age or older. The average household size was 2.31 and the average family size was 2.94.
In the county the population was spread out with 23.90% under the age of 18, 5.50% from 18 to 24, 23.90% from 25 to 44, 22.70% from 45 to 64, and 24.10% who were 65 years of age or older. The median age was 43 years. For every 100 females there were 96.60 males. For every 100 females age 18 and over, there were 92.50 males.
The median income for a household in the county was $26,524, and the median income for a family was $34,412. Males had a median income of $25,037 versus $16,946 for females. The per capita income for the county was $14,055. About 9.30% of families and 12.50% of the population were below the poverty line, including 12.40% of those under age 18 and 17.00% of those age 65 or over.