The Wind River Range is in the southern portion and contains Gannett Peak, the tallest mountain in Wyoming. Yellowstone National Park forms part of the boundary to the west; south of Yellowstone, the Continental Divide separates the forest from its neighbor Bridger-Teton National Forest to the west.he Clarks Fork of the Yellowstone River is federally-designated as a Wild and Scenic River for 22 mi (35 km) through the forest, with cliffs towering up to 2,000 ft (610 m) as the river winds through a gorge.