United States v. Willow River Power Co., 324 U.S. 499 (1945), is a 1945 decision of the U.S. Supreme Court involving the question whether the United States was liable under the Fifth Amendment for a "taking" of private property for a public purpose when it built a dam on navigable waters that raised the water level upstream to lessen the head of water at a power company’s dam, thereby decreasing the production of power by the company’s hydroelectric turbines.

Subsequently, the Willow River Power Company acquired the land adjacent to these dams and it built a hydroelectric facility near them.

Other damages that result from government conduct are absorbed by the public, if at all, only when Congress passes a law providing for compensation.

[4] The Court then stated the issue before it as follows: [N]ot all economic interests are "property rights;" only those economic advantages are "rights" which have the law back of them, and only when they are so recognized may courts compel others to forbear from interfering with them or to compensate for their invasion.

But that a closed catalogue of abstract and absolute "property rights" in water hovers over a given piece of shore land good against all the world is not, in this day, a permissible assumption.

The Court therefore ruled: We hold that claimant's interest or advantage in the high water level of the St. Croix River as a run-off for tail waters to maintain its power head is not a right protected by law, and that the award below based exclusively on the loss in value thereof must be reversed.