There are 7 US Post Offices in Bonneville County serving a total of 67,710 residents equating to 9,673 residents per post office. It's estimated that approximately 108,073 packages are handled across the 7 county post offices annually. Bonneville County is a county located in the U.S. state of Idaho. As of the 2010 census, the county had a population of 104,234, making it the fourth-most populous county in Idaho and the most populous in eastern Idaho. Its county seat and largest city is Idaho Falls. Bonneville County was established in 1911 and named after Benjamin Bonneville (1796\u20131878), a French-born officer in the U.S. Army, fur trapper, and explorer in the American West. Bonneville County is part of the Idaho Falls, ID Metropolitan Statistical Area. The county was partitioned from Bingham County, which was part of Oneida County until 1885."