There are 4 US Post Offices in Elmore County serving a total of 26,164 residents equating to 6,541 residents per post office. It's estimated that approximately 41,761 packages are handled across the 4 county post offices annually. Elmore County is a county located in the U.S. state of Idaho. As of the 2010 census, the population was 29,130. The largest city and county seat is Mountain Home. Elmore County comprises the Mountain Home, ID Micropolitan Statistical Area, which is also included in the Boise-Mountain Home-Ontario, ID-OR Combined Statistical Area."