There are 16 US Post Offices in Marathon County serving a total of 100,655 residents equating to 6,291 residents per post office. It's estimated that approximately 160,657 packages are handled across the 16 county post offices annually. Marathon County is a county located in the U.S. state of Wisconsin. As of the 2010 census, the population was 134,063. Its county seat is Wausau. It was founded in 1850, created from a portion of Portage County. At that time the county stretched to the northern border with the upper Michigan peninsula. It is named after the battlefield at Marathon, Greece. Marathon County comprises the Wausau, WI Metropolitan Statistical Area and is included in the Wausau-Stevens Point-Wisconsin Rapids, WI Combined Statistical Area."