On February 19, 1810, the Ohio government authorized the creation of Clinton County. The county took its name from George Clinton, the Vice-President of the United States in 1810. Many of the county's early residents were members of the Society of Friends (Quakers). They played an important role in the Underground Railroad during the 1830s, 1840s, 1850s, and 1860s, helping runaway slaves find freedom in the North. The Quakers also established Wilmington College during the 1870s.
Clinton County is located in southwestern Ohio. The county is primarily rural, with just over one percent of its 411 square miles deemed to be urban areas. Wilmington is the largest metropolitan area, with a population of 11,921 people in 2000. It is also the county seat and home to a National Weather Service station. In 2000, the county's next largest community was Blanchester, with a population of 4,220 people. Unlike many of Ohio's predominantly rural counties, Clinton County experienced more than a fourteen percent growth between 1990 and 2000, raising the county's total population to 40,543 residents. The county averages almost ninety-nine people per square mile.
Most Clinton County residents work in the transportation sector. In this order, manufacturing, sales, service industry, and government positions rank second, third, fourth, and fifth in employment opportunities for Clinton County residents. Agriculture ranks sixth, although the county consists of some of the most fertile and productive soil in the United States. In 1999, the per capita income was just under twenty-six thousand dollars, with nine percent of the population living in poverty.
Most voters in Clinton County claim to be independents, yet in recent years, they have overwhelmingly supported Republican Party candidates at the national level.