The Chillicothe Micropolitan Statistical Area includes all of Ross County.
2000 73,345 1990 69,330 1980 65,004 1970 61,211 1960 61,215 1950 54,424 1940 52,147 1930 45,181 1920 41,556 1910 40,069 1900 40,940 1890 39,454 1880 40,307 1870 37,097 1860 35,071 1850 32,074 1840 27,460 1830 24,068 1820 20,619 1810 15,514 1800 8,540
As of the census of 2000, there were 73,345 people, 27,136 households, and 19,185 families residing in the county. The population density was 106 people per square mile (41/km²). There were 29,461 housing units at an average density of 43 per square mile (17/km²). The racial makeup of the county was 91.74% White, 6.20% Black or African American, 0.31% Native American, 0.35% Asian, 0.02% Pacific Islander, 0.19% from other races, and 1.20% from two or more races. 0.58% of the population were Hispanic or Latino of any race.
There were 27,136 households out of which 32.70% had children under the age of 18 living with them, 55.20% were married couples living together, 11.10% had a female householder with no husband present, and 29.30% were non-families. 24.90% 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 2.50 and the average family size was 2.97.
In the county, the population was spread out with 24.00% under the age of 18, 8.60% from 18 to 24, 31.60% from 25 to 44, 23.60% from 45 to 64, and 12.20% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 108.30 males. For every 100 females age 18 and over, there were 109.00 males.
The median income for a household in the county was $37,117, and the median income for a family was $43,241. Males had a median income of $35,892 versus $23,399 for females. The per capita income for the county was $17,569. About 9.10% of families and 12.00% of the population were below the poverty line, including 15.10% of those under age 18 and 10.20% of those age 65 or over.