Juniata County was created on March 2, 1831, from part of Mifflin County and named for the Juniata River.
Its county seat is Mifflintown.
As of the census of 2000, there were 22,821 people, 8,584 households, and 6,463 families residing in the county. The population density was 58 people per square mile (22/km²). There were 10,031 housing units at an average density of 26 per square mile (10/km²). The racial makeup of the county was 98.05% White, 0.37% Black or African American, 0.14% Native American, 0.25% Asian, 0.17% Pacific Islander, 0.50% from other races, and 0.51% from two or more races. 1.62% of the population were Hispanic or Latino of any race. 45.4% were of German, 20.2% American, 5.7% Irish and 5.0% English ancestry according to Census 2000. 3.95% reported speaking Pennsylvania German, German, or Dutch at home; 1.63% speak Spanish.[1]
There were 8,584 households out of which 33.00% had children under the age of 18 living with them, 64.60% were married couples living together, 6.30% had a female householder with no husband present, and 24.70% were non-families. 21.10% of all households were made up of individuals and 10.50% had someone living alone who was 65 years of age or older. The average household size was 2.60 and the average family size was 3.01.
In the county, the population was spread out with 25.00% under the age of 18, 8.00% from 18 to 24, 28.10% from 25 to 44, 23.80% from 45 to 64, and 15.20% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 99.00 males. For every 100 females age 18 and over, there were 96.40 males.