While on the road, I always try and remember to pick up a postcard or two every place I stop. And though I've got more than I can count by now, my favorite remains this art deco number I picked up a few years ago at Carlsbad Caverns.
With minimal colors and organic, yet uncluttered lines, it portrays the majesty and scale of New Mexico's grand cave formations in a style that's unmistakably 1930s.
What I discovered much later was that this design was just one in a larger body of work commissioned by the Works Project Administration. From 1935 to 1943, the Federal Art Project hired artists to create numerous cultural and public-safety posters, which included several works encouraging citizens to visit the country's National Parks and natural wonders.
In a tangential activity that took up most of my afternoon, I perused the "By the People, For the People" archive at the Library of Congress, which holds more than 900 of the 2,000 WPA posters known to exist.
You can buy a number of them through the Library of Congress's online store.