 Between 1890 and 1940 , five dams were built in the vicinity of Great Falls to generate power from the Great Falls of the Missouri , a chain of giant waterfalls formed by the river in its path through western Montana . Black Eagle Dam , built in 1891 on Black Eagle Falls , was the first dam of the Missouri . <unk> in 1926 with a more modern structure , the dam was little more than a small weir atop Black Eagle Falls , diverting part of the Missouri 's flow into the Black Eagle power plant . The largest of the five dams , Ryan Dam , was built in 1913 . The dam lies directly above the 87 @-@ foot ( 27 m ) Great Falls , the largest waterfall of the Missouri . 
