Dry Tortugas National Park is one of the least visited national parks in the United States, with only 60,000 visitors per year. This is primarily due to its remote location 70 miles west of Key West. It is also the most aquatic of all the US national parks with 98% of the park consisting of water. The 2% of the park which is land is largely taken up by Fort Jefferson.
US National Parks Map - The World includes this great country too! I'm proud to say that my parents took us to so many of the National Parks when we were kids and I've added to the list as a grown up. Still more to see!