Natural Bridge Park near Natural Bridge, Alabama, preserves a dramatic natural arch formed about 200 million years ago as the New River wore away weaker sandstone and left a stronger span of sandstone and iron ore. Open to the public since 1954, the privately owned park features a bridge 60 feet high and 148 feet long, regarded as the longest natural arch east of the Rocky Mountains in North America. A two-mile trail passes beneath the arch and other formations, including an outcrop resembling the Indian Head nickel. The site also has older human significance, as Muscogee Creek Indians lived here and likely used the bridge-cave enclosure for shelter.