There are 7 US Post Offices in Lemhi County serving a total of 7,730 residents equating to 1,104 residents per post office. It's estimated that approximately 12,338 packages are handled across the 7 county post offices annually. Lemhi County is a county located in the U.S. state of Idaho. As of the 2010 census, the population was 7,936. The largest city and county seat is Salmon. The county was established in 1869, named after Fort Lemhi (or Limhi), a remote Mormon missionary settlement from 1855\u201358 in Bannock and Shoshone territory."