R. Robinson,People watching Old Faithful erupt from geyser cone, Yellowstone National Park, Wyoming, 1948.

R. Robinson,People watching Old Faithful erupt from geyser cone, Yellowstone National Park, Wyoming, 1948.

George Fiske, Overhanging Rock, Glacier Point, Yosemite Valley, California, 1910.

George Fiske, Overhanging Rock, Glacier Point, Yosemite Valley, California, 1910.

William Bell, Grand Canyon of the Colorado, mouth of Paria Creek, looking west from plateau, 1872.
Source: National Archives and Records Administration

William Bell, Grand Canyon of the Colorado, mouth of Paria Creek, looking west from plateau, 1872.

Source: National Archives and Records Administration

Ansel Adams, In Saguaro National Monument, Saguaro, Arizona, USA, 1941.

Ansel Adams, In Saguaro National Monument, Saguaro, Arizona, USA, 1941.

William Henry Jackson, The U.S. Geological and Geophysical Survey of the Territories, conducted by Hayden, en route with pack train upon the trail between the Yellowstone and East Fork Rivers, Yellowstone National Park, Wyoming, 1871.

William Henry Jackson, The U.S. Geological and Geophysical Survey of the Territories, conducted by Hayden, en route with pack train upon the trail between the Yellowstone and East Fork Rivers, Yellowstone National Park, Wyoming, 1871.

Ansel Adams, The Tetons and the Snake River, Grand Teton National Park, Wyoming, 1942.
Source:  National Archives and Records Administration, Records of the National Park Service

Ansel Adams, The Tetons and the Snake River, Grand Teton National Park, Wyoming, 1942.

Source: National Archives and Records Administration, Records of the National Park Service

“Cliff Palace, Mesa Verde National Park” by Ansel Adams. Mesa Verde, Colorado, USA, 1941.

“Cliff Palace, Mesa Verde National Park” by Ansel Adams. Mesa Verde, Colorado, USA, 1941.

John Muir in Yosemite Valley, 1912

John Muir in Yosemite Valley, 1912