The first American Falls dam, near the city of American Falls, Idaho, was built from 1925-1927. By 1975, it was so deteriorated that a second dam was built just downstream from the original. The second one was built in 1974-1978. The replacement dam was designed and constructed by Bechtel Corporation. The dam is operated by the Bureau of Reclamation and provides irrigation, flood control, power generation, recreation, and the improvement of fish and wildlife resources.
The city of American Falls was moved to its current location in 1925 before the original dam was constructed. The old site of the town was flooded when the reservoir filled, along with segments of the Oregon Trail. Some of the buildings of the old town can still be seen when the water is low.
Before the old dam was replaced, it faced a major challenge in 1976. The newly-constructed Teton Dam upriver collapsed as its reservoir filled. The American Falls Dam, downstream, was in danger; it would receive more water at one time than ever before. To protect it and other dams downstream, the outlet works were opened to their fullest and the reservoir was emptied. Two days later, the floodwaters reached the American Falls Dam, but they did not overcome its spillway.
Today, American Falls Dam plays an important role in the agricultural base of southern Idaho.