There are 4 US Post Offices in Mahnomen County serving a total of 5,748 residents equating to 1,437 residents per post office. It's estimated that approximately 9,174 packages are handled across the 4 county post offices annually. Mahnomen County (/m\u0259\u02c8no\u028am\u0259n/ m\u0259-NOH-m\u0259n) is a county located in the U.S. state of Minnesota. As of the 2010 census, the population was 5,413. Its county seat is Mahnomen. The entire county is part of the White Earth Indian Reservation. It is the only county in Minnesota entirely within an Indian reservation. The county, along with East Polk and Becker County, are one of the biggest cattle-raising areas in the northwestern part of Minnesota."