Buffalo County is part of the Kearney, Nebraska Micropolitan Statistical Area.
In the Nebraska license plate system, Buffalo County is represented by the prefix 9 (it had the ninth-largest number of vehicles registered in the county when the license plate system was established in 1922).
1860 - 114 1870 - 193 1880 - 7,531 1890 - 22,162 1900 - 20,254 1910 - 21,907 1920 - 23,787 1930 - 24,338 1940 - 23,655 1950 - 25,134 1960 - 26,236 1970 - 31,222 1980 - 34,797 1990 - 37,447 2000 - 42,259
As of the census of 2000, there were 42,259 people, 15,930 households, and 10,227 families residing in the county. The population density was 44 people per square mile (17/km²). There were 16,830 housing units at an average density of 17 per square mile (7/km²). The racial makeup of the county was 95.18% White, 0.55% Black or African American, 0.33% Native American, 0.68% Asian, 0.03% Pacific Islander, 2.20% from other races, and 1.03% from two or more races. 4.66% of the population were Hispanic or Latino of any race. 42.5% were of German, 8.1% Irish, 7.8% English, 6.8% American and 5.3% Swedish ancestry according to Census 2000.
There were 15,930 households out of which 32.70% had children under the age of 18 living with them, 52.90% were married couples living together, 8.30% had a female householder with no husband present, and 35.80% were non-families. 26.10% of all households were made up of individuals and 9.60% had someone living alone who was 65 years of age or older. The average household size was 2.48 and the average family size was 3.02.
In the county the population was spread out with 25.00% under the age of 18, 17.80% from 18 to 24, 26.60% from 25 to 44, 19.00% from 45 to 64, and 11.50% who were 65 years of age or older. The median age was 30 years. For every 100 females there were 96.00 males. For every 100 females age 18 and over, there were 92.40 males.
The median income for a household in the county was $36,782, and the median income for a family was $46,247. Males had a median income of $30,182 versus $21,977 for females. The per capita income for the county was $17,510. About 6.30% of families and 11.20% of the population were below the poverty line, including 10.50% of those under age 18 and 8.50% of those age 65 or over.