Great Smoky Mountains National Park preserves some of the last remaining virgin forests in the Appalachian Mountains. Home to black bear, deer, and many other forms of wildlife, the park is easily the most popular national park in the National Park Service, averaging over 9,000,000 visitors each year. The area preserves mountain terrain and diversity that have been living in the mountain environment for over 300,000,000 years, when the Appalachian Mountains were formed. The area is renowned for its diversity in both flora and fauna while also containing a popular segment of the ambitious Appalachian Trail, where it straddles the borders of North Carolina and Tennessee.