Not sure how this works, but it seems to jump the Great Divide fairly frequently. E.g. a click on the Idaho side of the Bitterroots will show "Salmon, Idaho" as

Not sure how this works, but it seems to jump the Great Divide fairly frequently. E.g. a click on the Idaho side of the Bitterroots will show "Salmon, Idaho" as the start point, but jump to a stream in Montana that ends up in the Gulf of Mexico. Cool visualization, but does not seem to respect actual drainage basins at the start point.