Isa Lake is located in Yellowstone National Park, in the U.S. state of Wyoming.[2] The lake straddles the continental divide at Craig Pass and was first discovered in 1891 by Hiram M. Chittenden, who was exploring the best routes for a road to connect Old Faithful and West Thumb geyser basins. Chittenden named the lake after Miss Isabel Jelke, from Cincinnati, though it is not clear why.[3][4]