Lake Nighthorse is a reservoir created by the 270 feet (82 m) high Ridges Basin Dam[1] southwest of Durango in La Plata County Colorado.

First authorized by the U.S. Congress on September 30, 1968 (Public Law 90-537),[3] the Animas-La Plata Water Project, as it came to be known, experienced a few decades of delays due in part to political concerns, farming claims, environmental challenges, cost overruns and government funding issues.

A breakthrough to the delays came with the Colorado Ute Settlement Act Amendments in December 2000 (Public Law 106–554).

[4] The Bureau of Reclamation began construction in 2003, with the reservoir filling to capacity on June 29, 2011, at a total cost of $500 million.

The lake is open as of April 1, 2018, for recreation, fishing and boating.