There are 8 US Post Offices in Fremont County serving a total of 7,173 residents equating to 897 residents per post office. It's estimated that approximately 11,449 packages are handled across the 8 county post offices annually. Fremont County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 7,441. The county seat is Sidney. The county was formed in 1847 and named for the military officer John C. Fremont."