There are 7 US Post Offices in Lyon County serving a total of 33,046 residents equating to 4,721 residents per post office. It's estimated that approximately 52,745 packages are handled across the 7 county post offices annually. Lyon County (standard abbreviation: LY) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 33,690. The county seat and largest city is Emporia. The county was named for General Nathaniel Lyon, who was killed at the Battle of Wilson's Creek in the Civil War."