Mercer County, Ohio

Mercer County is a county located in the U.S. state of Ohio. As of the 2010 census, the population was 40,814. Its county seat is Celina. The county was created in 1820 and later organized in 1824. It is named for Hugh Mercer, an officer in the American Revolutionary War.Mercer County comprises the Celina, OH Micropolitan Statistical Area, which is also included in the Lima-Van Wert-Celina, OH Combined Statistical Area.HistoryMercer County was founded in 1820 which set it apart from Darke County. Land south of the Greenville Treaty Line was still part of Darke County. An act establishing Mercer County took place on January 2, 1824. In 1837 Van Wert County was detached and the county line established is the current northern border of Mercer County. In 1839 Celina was established as the capital of Mercer County, St. Marys, Ohio was the previous capital. In 1848 the area south of the Greenville Treaty Line to the current southern county line, was attached. When Auglaize County, Ohio was formed, Mercer County's eastern border was moved 6 miles west with the exception of the area south of the Greenville Treaty line. This created the sharp point at Mercer County's south-east corner and was the last county line modification.