Circleville is a city in and the county seat of Pickaway County, Ohio, United States, along the Scioto River. The population was 13,314 at the 2010 census.The city was originally laid out after 1810 within the 1100-foot diameter of a circle of a Hopewell tradition earthwork dating to the early centuries of the Common Era. The county courthouse was built in the center of the innermost circle. By the late 1830s residents had tired of this design and gained authorization from the state legislature to change the layout to a standard grid, which was accomplished by the mid-1850s. All traces of the Hopewell earthwork were destroyed here, although hundreds of other monuments may be found in the Ohio Valley.HistoryBy the mid-18th century, the Lenape (Delaware Indians) were pushed west from Pennsylvania by English-led settlers flowing into the colony. The Lenape were given permission by the Wyandot to settle in the Ohio country. One of their settlements was Maguck, built by 1750 on the banks of the Scioto River. Modern Circleville was built to the north of this site.Noted frontier explorer Christopher Gist was the first recorded European visitor to the Circleville area. Gist reached Maguck, the small Lenape village of about 10 families on the east bank of the Scioto River, on January 20, 1751. He wrote that he had stayed in the town for four days.