On January 31, 1810, the Ohio government authorized the creation of Guernsey County. Residents named the county after the "Isle of Guernsey."
Guernsey County is located in eastern Ohio, in the heart of Appalachia. It is predominantly rural, with less than one percent of the county's 522 square miles consisting of urban areas. The county seat is Cambridge, which, in 2000, was the county's largest urban center with a population of 11,520 people. Guernsey County experienced a slight increase in population—roughly 4.5 percent—between 1990 and 2000, raising the total number of residents to 40,792 people. Many residents of Ohio's rural communities are seeking better lives and more opportunities in the state's cities, but Guernsey County seems to be remaining stable in population. The county averages seventy-eight people per square mile.
The largest employers in Guernsey County are service industries, such as health care and communications, with sales positions a close second. During the late nineteenth century, Guernsey County became famous for its glass manufacturing. While the county's glass production has declined, a tourist industry, consisting largely of glass collectors, has arisen in its place. In 1999, the per capita income in the county was 18,641 dollars, with 15.4 percent of the people living in poverty.
Most voters in Guernsey County claim to be independents, yet in recent years, they have supported Republican Party candidates at the national level by small margins.
Among Guernsey County's more prominent residents were astronaut John Glenn, Jr., and actor William Boyd, who played Hopalong Cassidy in movies and on television.