Knox County, Maine  Knox County is a county located in the state of Maine, in the United States. As of the 2010 census, the population was 39,736. Its county seat is Rockland. The county is named for American Revolutionary War general and Secretary of War Henry Knox, who lived in the county from 1795 until his death in 1806. The county was established on April 1, 1860, and is the most recent county to be created in Maine. It was carved from parts of Waldo and Lincoln counties. The Union Fair, started in 1868, began as the efforts of the North Knox Agricultural and Horticultural Society. According to the U.S. Census Bureau, the county has a total area of , of which is land and (68%) is water. It is the second-smallest county in Maine by land area. It was originally part of the Waldo Patent. At the 2000 census there were 39,618 people, 16,608 households, and 10,728 families living in the county. The population density was 108 people per square mile (42/km²). There were 21,612 housing units at an average density of 59 per square mile (23/km²). The racial makeup of the county was 98.28% White, 0.24% Black or African American, 0.22% Native American, 0.36% Asian, 0.01% Pacific Islander, 0.12% from other races, and 0.78% from two or more races. 0.57% of the population were Hispanic or Latino of any race. 25.4% were of English, 12.2% Irish, 11.7% United States or American, 7.5% German and 5.7% French ancestry. 97.1% spoke English and 1.5% French as their first language. Of the 16,608 households 28.30% had children under the age of 18 living with them, 52.20% were married couples living together, 9.00% had a female householder with no husband present, and 35.40% were non-families. 29.00% of households were one person and 12.70% were one person aged 65 or older. The average household size was 2.31 and the average family size was 2.83. The age distribution was 22.40% under the age of 18, 6.30% from 18 to 24, 27.40% from 25 to 44, 26.70% from 45 to 64, and 17.20% 65 or older.