Isolated 70 miles west of Key West, the islands of Dry Tortugas National Park appear to arise as if by magic, floating atop the waters of the Gulf of Mexico. Discovered by Juan Ponce de León over 500 years ago, Tortugas is North America's second-oldest persistent place name. The adjacent Florida Strait provided essential passageway for navies, ships of commerce, pirates, and privateers. Its reefs claimed hundreds of ships over the centuries. The nation's largest masonry fort, Fort Jefferson, secured Union control of the Florida Strait during the Civil War and served as the infamous prison for Dr. Samuel Mudd and other convicted Lincoln conspirators. Its waters, coral reefs, and aquatic life remain among the most biologically intact in North America. Seabird species nest here that nest nowhere else on the continent. The Tortugas has attracted generations of naturalists, scientists, fishermen, divers, birders, and other visitors. The islands and waters of the Dry Tortugas remain today remote, historic, and biologically pristine.