Progressive Farmer rated Union County 2nd in the 2006 "Best Place to Live" in the U.S., because "its schools are good, its towns neat and its people friendly."
As of the census of 2000, there were 12,584 people, 4,927 households, and 3,517 families residing in the county. The population density was 27 people per square mile (11/km²). There were 5,345 housing units at an average density of 12 per square mile (4/km²). The racial makeup of the county was 96.85% White, 1.34% Asian, 0.37% Native American, 0.01% Pacific Islander, 0.33% Black or African American, 0.24% from other races, and 0.87% from two or more races. 1.26% of the population were Hispanic or Latino of any race.
There were 4,927 households out of which 34.80% had children under the age of 18 living with them, 62.00% were married couples living together, 6.30% had a female householder with no husband present, and 28.60% were non-families. 24.20% of all households were made up of individuals and 10.30% had someone living alone who was 65 years of age or older. The average household size was 2.53 and the average family size was 3.02.
In the county, the population was spread out with 27.00% under the age of 18, 7.30% from 18 to 24, 28.40% from 25 to 44, 23.70% from 45 to 64, and 13.50% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 99.20 males. For every 100 females age 18 and over, there were 98.30 males.
The median income for a household in the county was $44,790, and the median income for a family was $51,227. Males had a median income of $35,406 versus $23,440 for females. The per capita income for the county was $24,355. About 3.70% of families and 5.50% of the population were below the poverty line, including 4.90% of those under age 18 and 10.70% of those age 65 or over.