One by one, they have created our collective memory of history — famous photos of the Civil War, Abraham Lincoln, the Hindenburg disaster, and the mother and her child that captured the despair of the Great Depression.
"These are all iconic images that are frozen in our memory and cannot be erased, even if we wanted to," says Els Rijper, curator of the Betteman photo archive.
But archivists have yet to find a way to save today's digital images for history, a way that will transcend the changes in technology and preserve the visual legacy of the 21st century for generations to come.
After all, conventional photography is now a thing of the past. Last year, more digital cameras were sold than conventional cameras. Last month, Kodak even announced it would stop making reloadable 35mm cameras in the United States and Europe.
Until a decade ago, pictures came from negatives and transparencies, something you could hold and file away.
Photos recorded the assassinations of President John F. Kennedy, with JFK Jr. saluting his father's casket; of Martin Luther King Jr., with a famous image of aides pointing toward the assassin; and of Robert F. Kennedy, his face struck by harsh light as he lay on the floor of the Ambasador Hotel kitchen in Los Angeles.
Famous images from Vietnam depict a disillusioned soldier, the summary execution of a Viet Cong suspect, a young girl running in terror from a napalm attack.
"Everyone remembers every single major historical event by a still image," says Mary Ann Golon, a picture editor who chooses the images for each week's Time magazine. "Still images last in a way that moving images don't."
Archives like Betteman, photo agencies like Corbis and Getty, and publications like Time all have worked painstakingly to preserve those frozen moments of the past.
Thanks to them, we remember what World War II looked like in images such as the U.S.S. Arizona burning at Pearl Harbor after the Japanese attack, the moment of triumph at Iwo Jima — when Marines raised the American flag on Mount Suribachi — and the uninhibited joy of a sailor kissing a nurse in New York's Times Square the day the war ended.
Remembering the digital age may not be so easy. Photos are becoming a series of electronic impulses captured for a moment on cards or discs. And there is no certainty that digital images will survive for future generations.
Golon worries about what has already been lost.
"At the very beginning of the digital era, we had forms of storage for these photographs that were not a transparency, not a negative, that are completely obsolete forms of technology," she says.
Rijper edited Kodachrome, a book based on 60-year-old color photos never before seen — including images of Hitler's 50th birthday party, black sharecroppers in a cotton field and the liberation of World War II's Buchenwald death camp. Some of those images might not have survived in a digital world.
"It is more instant," Rijper says. "And you can delete instantly, as well."
Unlike conventional film, most digital photos are edited on the spot. Not every photo of an event is preserved.
A case in point may be a picture of Monica Lewinsky and Bill Clinton taken at a White House function, apparently confirming she was more than just an intern.
"Most of the photographers who were there at the time considered that image was not valuable," Rijper says. "They didn't know what to do with it. They deleted it."
But Time's Dirck Halstead was shooting film, not digital images, and his photo was saved. It was retrieved and became the magazine's cover when the scandal broke.
"If you somehow don't figure out a way to make sure you are retaining this visual narrative of history and our lives, it is a huge loss for everyone," Golon says.