Great Smoky Mountains National Park

24. Great Smoky Mountains National Park - 9 million visitors. With more than 9 million visitors per year, the Great Smoky Mountains national park is the most visited national park in the united states by far, and one of the most popular attractions in the US in general. The park is located in the states of Tennessee and North Carolina and was established in 1934. This UNESCO world heritage site is home to over than 400 vertebrate species, 100 tree species, and 5000 plant species. The main attraction of the park is hiking, offering over 800 miles (1,300 km) of trails