Isa Lake, Lake in Yellowstone National Park, United States
Isa Lake is a mountain lake in Yellowstone National Park situated directly on the Continental Divide at an elevation of about 8,300 feet (2,530 meters). It sits between the Old Faithful and West Thumb geyser basins along the main park roadway.
The lake was discovered in 1891 by engineer Hiram M. Chittenden while surveying routes between the geothermal areas. It was named in honor of Isabel Jelke, a young woman from Cincinnati.
The Yellowstone region where Isa Lake stands has been home to multiple Indigenous Nations, including the Nimíipuu, Absaroke, and Shoshone for over 11,000 years.
The lake sits right along the main road between Old Faithful and West Thumb and is easily accessible by car. The area remains open year-round, though snow and ice in winter can affect driving conditions.
What makes this lake unusual is its rare drainage pattern: water from the eastern side flows toward the Pacific Ocean, while water from the western side flows toward the Atlantic Ocean. Despite its small size, the water divides between two great oceans.
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