Oneida County was created by the state legislature in 1887 from land that had been part of Lincoln County; essentially the legislature split Lincoln County and the northern part became Oneida County. In 1893 the legislature acted again and split Oneida County: the northern portion became Vilas County. There were some relatively minor boundary changes in 1901 and 1905 as well. Oneida County was named after the Oneida tribe of Native Americans. The Oneida are one of the Five Nations of the Iroquois.
The county seat is the City of Rhinelander. The original settlement was named Pelican Rapids – the Pelican River joins the Wisconsin River at this point. The story of modern Rhinelander begins around 1870 when the Brown brothers (Anderson and Webster) convinced their father and uncle to buy land in the area with the intent of opening a sawmill to utilize the pine forests nearby and further north along the two rivers. Webster Brown eventually became the first mayor of Rhinelander. The town was named after Frederic Rhinelander who happened to be the president of a railroad company; this was part of the Brown’s plan to secure a railroad line for their lumber business. They did have to sell some of their land holdings to the railroad, but the railroad reached Rhinelander in 1882. This is how Rhinelander became the hub of economic activity in the area.
The Oneida County courthouse is located at 1 South Oneida Avenue in Rhinelander. The courthouse is on the National Register of Historic Places. It was constructed between 1908 and 1910 in the Neoclassical style with a large octagonal dome.