There are 6 US Post Offices in Fremont County serving a total of 12,103 residents equating to 2,017 residents per post office. It's estimated that approximately 19,318 packages are handled across the 6 county post offices annually. Fremont County is a county located in the U.S. state of Idaho. As of the 2010 census the county had a population of 13,242. The county seat and largest city is St. Anthony. The county was established in 1893, and was named for the explorer John C. Fr\u00e9mont. Fremont County is part of the Rexburg, ID Micropolitan Statistical Area, which is also included in the Idaho Falls-Rexburg-Blackfoot, ID Combined Statistical Area."