Donald A. Wollheim organized the first American science fiction convention on the 22nd of October 1936 when he was twenty-two years old. This gathering took place in Philadelphia and included groups from New York and Philadelphia.
Donald A. Wollheim founded DAW Books with his wife Elsie Balter Wollheim upon leaving Ace in 1971. DAW claimed to be the first mass market specialist science fiction and fantasy fiction publishing house and issued its first four titles in April 1972.
Donald A. Wollheim published an unauthorized paperback edition of J. R. R. Tolkien's The Lord of the Rings because no large American publisher would release fantasy before the 1960s. This became the first mass-market paperback edition of Tolkien's epic despite later legal disputes regarding copyright violations.
Donald A. Wollheim joined the New York Science Fiction League and formed a group that successfully sued Hugo Gernsback for unpaid story payments. He also founded the Fantasy Amateur Press Association in 1937 and established the Futurians club in 1938 which shifted focus to writing and editing workshops after 1940.
Donald A. Wollheim actively practiced cross-dressing as a woman throughout his life and regularly attended events at Casa Susanna in the Catskills of upstate New York. He wrote about these experiences under the pseudonym Darrell G. Raynor in the book A Year Among the Girls which appeared in 1966.