Horseshoe Bend is the largest city in rural Boise County, in the southwestern part of the U.S. state of Idaho. Its population of 707 at the 2010 census was the largest in the county, though down from 770 in 2000.It is part of the Boise City–Nampa, Idaho Metropolitan Statistical Area. It is named for its location at the horseshoe-shaped U-turn of the Payette River, whose flow direction changes from south to north before heading west to the Black Canyon Reservoir.