For every Old Faithful and Grand Canyon of the Yellowstone, there's a host of other obscure places like The Gumper, Lactose ...

Editor’s Note: This story accompanies the May 2016 issue of National Geographic magazine, devoted entirely to America’s first national park. Find more at natgeo ...

Yellowstone National Park offers unique ... Mud Volcano is home to some of the park’s most acidic geothermal features. There ...