The Isa Lake Viewpoint, located about 8 miles east of the Old Faithful Area along the Grand Loop Road in Yellowstone National Park, is not a terribly exciting place. On the way to the Old Faithful geyser, you can alight from your vehicle and stand on the edge of a thin sliver of water filled with waterlilies and fallen logs. By the side of the lake is a Continental Divide elevation sign, and an interpretive sign describing the significance of the Continental Divide and Isa Lake.

‘Continental divide’ is a geographical divide on a continent, often in the form of a mountain ridge, such that rivers and lakes on one side of the divide drain into one ocean or sea, and those on the other side drain into another. Isa Lake straddles the continental divide of North America, standing at over eight thousand feet at the upper watershed for two of America’s most extensive drainage systems— the Snake and Columbia Rivers, and the Missouri and Mississippi.

Photo credit: Firas Wehbe/Flickr