Yellowstone National Park is the premier wildlife viewing area in the continental United States, and wildlife can be seen anywhere in the park. The most popular area for hard-core wildlife fans is the Lamar Valley in the remote northeastern corner of the park. For those with less time to drive just to see wildlife, a great alternative is the Hayden Valley along the main park loop road between Fishing Bridge Village and Canyon Village.
The big highlight of Hayden Valley is the large number of bison there, second only in numbers to the Lamar Valley. Bison are always seen here, often very close to (or right on) the road. For lucky visitors, one of the most spectacular sights to be seen in the park is a bison herd crossing the Yellowstone River in Hayden Valley. Elk are numerous, and bears are sometimes seen, including grizzlies. Coyotes are also often seen here as well.
There are numerous overlooks along the valley, and the best bet is to look for lots of cars and people with spotting scopes out. The wildlife hunters know where to go and when, and they will usually let you look through their scopes if they have something in their sights. As always, early morning and late afternoon/evening are the best times to see the more elusive animals.