Question: The Tongue River Dam impounds a  tributary that is approximately how many miles long?
Sentence (from "Tongue River (Montana)"): Most of the course of the river is through the beautiful and varied landscapes of eastern Montana, including the Tongue River Canyon, the Tongue River breaks, the pine hills of southern Montana, and the buttes and grasslands that were formerly the home of vast migratory herds of American bison.
Relevant evidence: No