As the National Park Service prepares to celebrates its centennial in August, the national parks have never been more popular.Total recreational visits to all NPS sites topped 300 million in 2015, an astounding 14 million increase from 2014. (In addition to the national parks, NPS sites include national historic sites, national monuments, national lakeshores and seashores, and so on.) Homing in on just the 58 national parks that reported visitation in 2015, recreational visits1 totaled 75.3 million, besting the 1997 record of 69.5 million.I’ve contributed to this trend, having visited 12 national parks in 15 visits since 2004.