Zion National Park, ca. 1938 by Ranger Naturalist Service Lassen Volcanic National Park, ca. 1938 by Ranger Naturalist Service Yellowstone National Park, ca. 1938 by Ranger Naturalist Service Zion National Park, ca. 1938 by Ranger Naturalist Service Lassen Volcanic National Park, ca. 1938 by Ranger Naturalist Service Yellowstone National Park, ca. 1938 by Ranger Naturalist Service