On December 6, 1800, the Northwest Territory authorized the creation of Clermont County. The county took its name from the French phrase for "clear mountain." President Ulysses S. Grant was born in Clermont County and his birthplace is now the site of a state memorial operated by the Ohio History Connection. Ohio Governor John M. Pattison also resided in the county. In 1797, Francis McCormick founded the first Methodist Church in Ohio at Milford. Many Clermont County residents played an important role in the Underground Railroad and helped runaway slaves find freedom in the North.
Clermont County is located in southwestern Ohio, and its southern border is on the Ohio River. The city of Cincinnati or its suburbs cover a portion of the county's 394 square miles. The county's largest township is Union Township with a population of 42,332 people in 2000. The largest village is Milford, with a population of 6,249 people in 2000. Clermont County experienced tremendous growth between 1990 and 2000, as many residents of Cincinnati moved away from the busyness of this major city. Between 1995 and 2000, approximately eleven thousand people moved to Clermont County, increasing the county's population to 177,977 residents. The county averages 394 people per square mile. The Village of Batavia is the county seat.
Most Clermont County residents work in Cincinnati. Residents employed in the county usually work in sales, manufacturing, or service industries. In 1999, the per capita income was just over twenty-six thousand dollars, with less than seven percent of the population living in poverty.
Most voters in Clermont County claim to be independents.