Salmon Falls Dam

Salmon Falls Dam is a dam constructed across Salmon Falls Creek in Twin Falls County, Idaho, in the United States. Located about 28 mi southwest of Twin Falls, the masonry arch-gravity dam is 217 ft high and 450 ft long, impounding up to 230650 acre feet of water in Salmon Falls Creek Reservoir. When full, the reservoir extends for 17 mi upstream, encompassing 3400 acre. The dam and reservoir control runoff from a drainage basin of 1610 mi2.

The dam was built in 1910 to provide irrigation water storage, and is owned and operated by the Salmon River Canal Company. A secondary purpose is flood control: the dam has spilled floodwaters twice, in 1984 and 2017. Salmon Falls Creek Reservoir is also a popular recreational lake, and is considered one of the best fisheries in southern Idaho.

The dam was the third-largest dam in the world at the time of its construction. It was part of a major reclamation effort which partly failed due less water being available than planned, partly due to unexpected leakage of water through the lava rock used in the dam's construction.

The Milner Dam (1904) was more successful.

The Salmon Falls Tract, the associated reclamation project, was originally termed the Salmon River Tract, and the dam was named the Salmon Dam. That naming "was chosen over Salmon Falls because the project promoters believed it had more appeal, although the dam’s name was changed back to Salmon Falls".

Historic site
The Salmon Falls Dam was listed on the National Register of Historic Places in 2009. The listing included a contributing building and six contributing structures in addition to the dam itself, on 10 acre. The dam's engineer was Andrew J. Wiley. The historic listing includes the dam, one building, and seven other structures.