There are 7 US Post Offices in Winneshiek County serving a total of 20,318 residents equating to 2,903 residents per post office. It's estimated that approximately 32,430 packages are handled across the 7 county post offices annually. Winneshiek County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 21,056. The county seat is Decorah.