Tennessee, North Carolina
Visitors in 2009 (through August): 6.4 million
Great Smoky Mountains National Park, which sits between North Carolina and Tennessee, is a wonderland of waterfalls, wildflowers and wildlife. It offers visitors 800 miles of maintained trails where they may see bears, turkeys, woodchucks, raccoons and even elk, which were reintroduced to the park in 2001. It is home to more than 1,660 kinds of flowering plants, more than any other national park in America, earning it the moniker "the wildflower park."
More info: nps.gov/grsm
Related:Randy Brown / Associated Press