Holmes County is a county in the U.S. state of Ohio. As of the 2020 Census, the population was 44,223. Its county seat is Millersburg. The county was formed in 1824 from portions of Coshocton, Tuscarawas and Wayne counties and organized the following year. It was named after Andrew Holmes, an officer killed in the War of 1812.Holmes County, which was about 42% Amish in 2010, and 48% in 2020, has the highest concentration of Amish in the world, which draws many visitors to the county.