According to the LOC's statement today (March 20), the archives include 50,000 prints and 525,000 negatives and slides from Adelman's career, gifted by an anonymous donor. Librarian Carla Hayden recognized Adelman's accomplishments during a ceremony earlier today.
As noted in his 2016 obituary in The New York Times, Adelman studied photography with Harper's Bazaar art director Alexey Brodovitch and Jacques Lowe, President John F. Kennedy's official photographer. In the early 1960s, he volunteered with the Congress of Racial Equality to document protests. That access allowed him to capture images of leaders like Rosa Parks and Martin Luther King Jr., as well as moments like the first Women's Liberation March in New York City and protesters being sprayed by fire hoses at an action in Birmingham.
"The hoses were so powerful that people were knocked down and propelled 15 or 20 feet," Adelman told The Guardian in 2008. "But instead of running away, some began to hold on to each other and stand up. I was hiding behind a tree—to protect my person and keep my camera dry. I managed to shoot several rolls with a Nikon F and a telephoto lens, even though I was appalled, frightened and very upset. I tried to find that moment when the water and the people were both readable and formed some sort of a pattern."
Here is that image and a few others, courtesy of the LOC: