Franklin County's population was estimated to be 26,513 in the year 2006, an increase of 1639, or +6.6%, over the previous six years; it has the fifth fastest growing population in the state.
As of the U.S. Census in 2000, there were 24,784 people, 9,452 households, and 6,720 families residing in the county. The population density was 43 people per square mile (17/km²). There were 10,229 housing units at an average density of 18 per square mile (7/km²). The racial makeup of the county was 95.05% White, 1.21% Black or African American, 0.94% Native American, 0.31% Asian, 0.78% from other races, and 1.71% from two or more races. Hispanic or Latino of any race were 2.62% of the population.
There were 9,452 households out of which 34.70% had children under the age of 18 living with them, 58.10% were married couples living together, 8.90% had a female householder with no husband present, and 28.90% were non-families. 24.80% of all households were made up of individuals and 11.30% had someone living alone who was 65 years of age or older. The average household size was 2.56 and the average family size was 3.04.
In the county the population was spread out with 27.50% under the age of 18, 8.90% from 18 to 24, 28.30% from 25 to 44, 21.20% from 45 to 64, and 14.00% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 98.30 males. For every 100 females age 18 and over, there were 94.10 males.
The median income for a household in the county was $39,052, and the median income for a family was $45,197. Males had a median income of $31,223 versus $22,992 for females. The per capita income for the county was $17,311. About 5.60% of families and 7.70% of the population were below the poverty line, including 8.40% of those under age 18 and 7.30% of those age 65 or over.