As the National Park Service marks its 100th birthday in 2016, TIME celebrates America’s spectacular, unspoiled natural treasures. Vast in scale at nearly 85 million acres, the park system stretches from Acadia park in Maine to War in the Pacific park on Guam and more than 400 parks in between, visited by 280 million people each year. Highlights of this special edition: * Jewels in the crown: a lavish pictorial tour of the most breathtaking parks, including Yosemite, Yellowstone, Grand Canyon, Glacier and Grand Teton * Founding fathers: the idea of a national park began with Western painter George Catlin and was later embraced by President Teddy Roosevelt after three nights under the stars in Yosemite Valley * A visitor’s guide to the best of the parks and monuments, from the spectacular to the quirky