There are 8 US Post Offices in Oneida County serving a total of 31,634 residents equating to 3,954 residents per post office. It's estimated that approximately 50,491 packages are handled across the 8 county post offices annually. Oneida County is a county in the state of Wisconsin, United States. At the 2010 census, the population was 35,998. Its county seat is Rhinelander.