There are 8 US Post Offices in Washburn County serving a total of 18,169 residents equating to 2,271 residents per post office. It's estimated that approximately 29,000 packages are handled across the 8 county post offices annually. Washburn County is a county in the U.S. state of Wisconsin. It is named after Governor Cadwallader C. Washburn. As of the 2010 census, the population was 15,911. Its county seat is Shell Lake. The county was created in 1883."