It’s a ubiquitous part of visiting a national park—a rectangular brochure with a distinctive black-and-white top that orients you to the treasures you can find inside. The iconic souvenirs are almost as much a staple of America’s national parks system as rangers and outdoor adventures.

Each of the park pamphlets follow a “Unigrid” design format developed in the 1970s. The format was invented to make design easy, minimize waste, and work horizontally or vertically. The brochures got their iconic look by none other than the acclaimed designer Massimo Vignelli, who is perhaps best known for designing New York’s subway signage and a subway map that made New Yorkers scratch their heads during the 1970s. Vignelli’s Helvetica-helmed Unigrid design is so iconic that it’s even in the collection of the Museum of Modern Art—not bad for a deceptively simple brochure.

Now, the maps have started to generate their own fanbase, writes National Parks Traveler’s Scott Johnson, including one man who created his own website to collect and share them. The website, National Park Maps, states its purpose right up front: “Here, I uploaded a bunch of free maps for you. Wooo!” It’s the brainchild of Matt Holly, a park ranger who works for the National Park Service’s National Resource Stewardship and Science Directorate, a division that helps the parks manage their natural resources.

Johnson interviewed Holly, who told him that he began to work on the site during the 2013 government shutdown in a bid to digitize the paper maps he’s come to love so much. “Nothing compares to unfolding the map, spreading it out on the table, and plotting your day’s adventure,” he tells Johnson.

So far, Holly has digitized over 1,000 maps from 93 of the 411 Park Services locations. Holly isolates the map parts of park publications for would-be visitors and even makes interactive versions. But some might argue that it’s hard to improve upon the beloved brochures themselves.

Can you guess the most popular map on Holly’s site? If your answer was Yellowstone, you’d be wrong—the park doesn’t even show up on the top ten list. The No. 1 spot goes to Bryce Canyon, the Utah reserve covered in hoodoos and filled with hikers enjoying the scenery. Whether you prefer to prep online or just wait for the brochure at the park, the maps and publications add even more eye candy to an amazing national resource.