American Falls is a city in and the county seat of Power County, Idaho, United States.American Falls was a landmark waterfall on the Snake River, named after a party of American trappers whose boat went over the falls. The Wilson Price Hunt expedition in 1811 camped at the falls one night and the expedition of John C. Fremont was here in 1843. The Oregon Trail passed north of town, through the present-day reservoir. Power plants first sprang up at the falls in 1901. American Falls was the first town in the U.S. to be entirely relocated; it was moved in 1925 to facilitate construction of the nearby American Falls Dam. The old townsite sits at the bottom of the reservoir, northeast of the present city. A larger dam was completed in 1978, downstream from the deteriorating 1927 structure, which was later demolished. American Falls is a city in and the county seat of Power County, Idaho, United States.