Clark County is a county in the U.S. state of Wisconsin. As of the 2020 census, the population was 34,659. Its county seat is Neillsville. By the early 1800s, the land and streams that are now Clark County were the hunting grounds of Chippewa, Dakota, Ho-Chunk and possibly Menominee peoples. In 1836 these Indians were joined by a party of French-Can…Clark County is a county in the U.S. state of Wisconsin. As of the 2020 census, the population was 34,659. Its county seat is Neillsville. By the early 1800s, the land and streams that are now Clark County were the hunting grounds of Chippewa, Dakota, Ho-Chunk and possibly Menominee peoples. In 1836 these Indians were joined by a party of French-Canadian fur traders who started a temporary post for the American Fur Company on the Black River's East Fork.