The trip spans just a hair under 14,500 miles, from Acadia National Park in Maine to Redwood National and State Parks in California. Olson estimates it would take about two months to run the circuit, depending on your tolerance for long driving days.
The trip omits places National Monuments (sorry, Devil's Tower) and National Historic Sites (sorry, Ford's Theatre) that are under the management of the National Park Service but aren't property considered national parks.
The difference between a "national park" and a "national monument" can come down to a simple matter of politics; the creation of a national park requires an act of Congress, according to the Sierra Club, while a president can declare a national monument without Congress under the Antiquities Act. Many of our most well-known national parks, such as Grand Canyon and Death Valley, started out as monuments.
Calculating the shortest path through every national park in the Lower 48 is no easy task. If you're a giant dork, you may recognize this as an instance of the Traveling Salesman Problem that looms large in computer science: Given X number of points, what's the shortest route you can take that passes through all of them?
In an earlier version of this map, Olson computed the shortest trip that would pass through one landmark in each of the Lower 48, plus one in the District of Columbia and a second site in California (for 50 landmarks). Other creative applications have included trips to all of America's top-rated breweries, and a 215,000 mile trip through all 37,000 Zip codes in the contiguous United States. And of course, the data-driven way to solve every Where's Waldo book.
Of course, the likelihood of anyone actually taking one of these mega-trips seems slim (if you do it, drop me a line). But the latest national parks trip seems quite a bit more practical than most, considering how many people plan epic road trips out west to visit multiple parks in a few weeks time.
If you're planning one of these trips for August, give Olson's map a gander before you hit the road.