Ansel Adams, the late American photographer and conservationist, was born on Feb. 20, 1902. His sweeping images of U.S. landscapes helped galvanize the country's nascent conservation movement last century, part of a decades-long effort to expand the national park system and popularize the idea of preserving wilderness.

This legacy warrants some reflection on his birthday — and since a picture is worth a thousand words, here are about 10,000 "words" to honor Adams' historic contributions to nature conservation:

Snake River, Grand Teton National Park, Wyoming

Canyon de Chelly National Monument, Arizona

Jackson Lake, Grand Teton National Park, Wyoming

Leaves in Glacier National Park, Montana

Rocky Mountain National Park, Colorado

Crystal Spring, Carlsbad Caverns National Park, New Mexico

Castle Geyser Coye, Yellowstone National Park, Wyoming

McDonald Lake, Glacier National Park, Montana

Saguaro National Monument, Arizona

Unnamed peak, Kings Canyon National Park, California

To see more of Adams' indelible imagery from U.S. national parks and monuments — mainly from 1941 to 1942, when he was working under a federal contract — check out these collections kept by the National Archives and the Interior Department.

All photos courtesy U.S. National Archives

Russell McLendon ( @russmclendon ) writes about humans and other wildlife.

Happy birthday, Ansel Adams
In honor of the famed photographer's birthday, here are 10 of his most awe-inspiring photos from the U.S. National Archives.