There are 5 US Post Offices in Franklin County serving a total of 12,634 residents equating to 2,527 residents per post office. It's estimated that approximately 20,165 packages are handled across the 5 county post offices annually. Franklin County is a county located in the U.S. state of Idaho. As of the 2010 Census the county had a population of 12,786. The county seat and largest city is Preston. The county was established in 1913 and named after Franklin D. Richards, an Apostle of The Church of Jesus Christ of Latter-day Saints. It is the only Franklin County in the United States that is not named after Benjamin Franklin. Franklin County is part of the Logan, UT-ID Metropolitan Statistical Area. The Bear River Massacre took place in present-day Franklin County on January 29, 1863."