At over 310,000 acres, the Grand Teton National Park lies just south of Yellowstone in northwestern Wyoming. It is home to the Teton mountain range, the youngest range in the Rockies, as well as most of the Jackson Hole valley. The park was originally established in 1929 when the boundary included most of the peaks and lakes around their base. It was later expanded in 1950 to add the valley floor. Grand Teton is known for its pristine ecosystem which allows for its world renowned trout fishing and mountaineering.