There are 6 US Post Offices in Aitkin County serving a total of 15,608 residents equating to 2,601 residents per post office. It's estimated that approximately 24,912 packages are handled across the 6 county post offices annually. Aitkin County (/\u02c8e\u026ak\u1d7bn/ AY-kin) is a county located in the U.S. state of Minnesota. As of the 2010 census, the population was 16,202. Its county seat is Aitkin. A portion of the Mille Lacs Indian Reservation is in the county. The county was created in 1857 and organized in 1871.