The materials in the collection primarily start in the early 1950s and span through the death of Poul in 2001 and Karen in 2018. There is extensive material pertaining to Poul’s writing career as well as research and background materials that supported it. There are also materials related to Karen's writing that includes poetry, short stories, co-authored works with Poul, and plays and filk operettas that she wrote or staged. The collection documents the Anderson’s broader involvement with science fiction fandom (primarily fanzines and convention materials), the Society for Creative Anachronism, and Sherlockiana groups. Notable correspondence includes a lengthy exchange between Poul and Karen in 1952-1953, letters from Robert Heinlein in the early 1960s, correspondence from Anthony Boucher to Karen Anderson, and letters between Karen and Astrid and the cast and creators of Star Trek in the 1960s. The collection includes a significant quantity of art, memorabilia, and awards.