In 2016, Randy Olson - a researcher at the University of Pennsylvania – created a map that routed the shortest possible road trip passing through every national park in the US. Olson estimated that the trip would take about two months to complete but didn’t allow for stopping at all the sites. If you plan on doing this route, plan for three months so you can stop and enjoy each park. Note: The map didn’t include parks that were inaccessible by car, and thus left out 12 parks in Hawaii, Alaska, American Samoa, and the Virgin Islands. If you plan to visit all 47 national parks – including the ones outside of the contiguous United States, anywhere from 6 months to a year would be best. Anything less would mean you don’t get to enjoy time in each national park.