There are 9 US Post Offices in Jackson County serving a total of 13,490 residents equating to 1,499 residents per post office. It's estimated that approximately 21,532 packages are handled across the 9 county post offices annually. Jackson County (county code JA) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 13,462. Its county seat and most populous city is Holton. The county was named for President Andrew Jackson. The Prairie Band Potawatomi Indian Reservation, located near the center of the county, comprises about 18.5% of the county's area."