There are 6 US Post Offices in Dakota County serving a total of 21,688 residents equating to 3,615 residents per post office. It's estimated that approximately 34,616 packages are handled across the 6 county post offices annually. Dakota County is a county in the U.S. state of Nebraska. As of the 2010 census, the population was 21,006. Its county seat is Dakota City. Dakota County is part of the Sioux City, IA\u2013NE\u2013SD Metropolitan Statistical Area. In the Nebraska license plate system, Dakota County is represented by the prefix 70 (it had the 70th-largest number of vehicles registered in the county when the license plate system was established in 1922). In August 2009, the Dakota County Board of Commissioners reversed an decision to abandon this system for alphanumeric plates upon introduction of new license plates in 2011. Douglas, Lancaster, and Sarpy Counties remain the only counties with alphanumeric plates in the state."