Last year was a record-breaking one in terms of visits to America’s national parks, the country’s “best idea.” There were 331 million recreation stays—a third consecutive all-time attendance record for the National Park Service (NPS). Even the parks that got the least number of tourists in previous years were more popular. In some cases, the difference even doubled. “The concept of ‘least visited’ is tricky since there are lots of factors that go into that,” Elizabeth Stern, National Partnerships Communications Coordinator at the National Park Service (NPS), says. “Some parks don’t have the ability to measure visitation, and some parks don’t have the same facilities." The following list is based on data provided by the NPS.