When the Corps of Engineers was busy building dams, especially to control the flow of the Missouri River, but also other rivers such as the Colorado, the Columbia and many other less significant rivers, one significant dam that was never built was a dam on the Yellowstone River. That would have reduced or even have eliminated the damage that has occurred in the interim years from various floodings. This dam was proposed to be built above Livingston. It would have controlled the flow of the Yellowstone during dry, hot years to provide a higher minimum flow that would have been beneficial to fish such as trout which do not thrive in warm water. Also, additional low cost hydroelectric power would have been provided, especially for the citizens of Montana right at that dam and at any other dams that are located downstream.
The only ones, as I see it, who feel it is beneficial to still have the longest river without a dam on it are people with a weird sense of values. Water held in reservoirs for use when needed has ever increasing value, even in the USA.
Walter Reed Heald