Great Smoky Mountains National Park straddles the Tennessee-North Carolina border and is the most-visited U.S. national park, drawing over 14 million annually. Spanning 522,000 acres of ancient Appalachian wilderness, it’s a UNESCO World Heritage Site famed for its biodiversity (over 19,000 species, including 100+ tree types), mist-shrouded peaks, and historic pioneer settlements.
Best Time: Spring (wildflowers), fall (foliage), or summer (cooler at elevation). Free entry; parking tags required ($5–$15).