The Great Smoky Mountains National Park draws more visitors than any other park in the nation. The park has some of the highest, oldest, and most picturesque mountain peaks and ridges in the eastern United States and more than 800 miles of hiking trails. These mountains, rivers, and scenic gorges constitute a formidable barrier between Tennessee and North Carolina. The struggle to acquire the land for the park from 10 large lumber companies and hundreds of small landholders started in 1923 and lasted more than 15 years. More than half of the 500,000 acres acquired for the park had been logged before the park's dedication in 1940, but thousands of acres of oldgrowth forest still survive. One of the most biologically diverse regions in North America-with thousands of species of plant and animal life, including 125 species of native trees-the park was designated an International Biosphere Reserve by the United Nations in 1976 and a World Heritage Site in 1983.