There are 5 US Post Offices in Osborne County serving a total of 3,890 residents equating to 778 residents per post office. It's estimated that approximately 6,209 packages are handled across the 5 county post offices annually. Osborne County (standard abbreviation: OB) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 3,858. The largest city and county seat is Osborne."