Bonneville County, in southeast Idaho, is part of the Upper Snake River Valley. Its eastern border is also the state border of Idaho and Wyoming. Idaho Falls, originally called Eagle Rock, is the county seat. Incorporated cities include Ammon, Idaho Falls, Iona, Irwin, Swan Valley, and Ucon. Bonneville is the fourth largest county in the state with a population of more than 104,000. Browse the listings and give a Real Estate of Star Valley agent a call for details.