Unknown (also known as Unknown Worlds) was an American pulpfantasy fiction magazine, published from 1939 to 1943 by Street & Smith, and edited by John W. Campbell. Unknown was a companion to Street & Smith's science fiction pulp, Astounding Science Fiction, which was also edited by Campbell at the time; many authors and illustrators contributed to both magazines. The leading fantasy magazine in the 1930s was Weird Tales, which focused on shock and horror. Campbell wanted to publish a fantasy magazine with more finesse and humor than Weird Tales, and put his plans into action when Eric Frank Russell sent him the manuscript of his novel Sinister Barrier, about aliens who own the human race. Unknown's first issue appeared in March 1939; in addition to Sinister Barrier, it included H. L. Gold's "Trouble With Water", a humorous fantasy about a New Yorker who meets a water gnome. Gold's story was the first of many in Unknown to combine commonplace reality with the fantastic.
Campbell required his authors to avoid simplistic horror fiction and insisted that the fantasy elements in a story be developed logically: for example, Jack Williamson's "Darker Than You Think" describes a world in which there is a scientific explanation for the existence of werewolves. Similarly, L. Sprague de Camp and Fletcher Pratt's Harold Shea series, about a modern American who finds himself in the worlds of various mythologies, depicts a system of magic based on mathematical logic. Other notable stories included several well-received novels by L. Ron Hubbard and short stories such as Manly Wade Wellman's "When It Was Moonlight" and Fritz Leiber's "Two Sought Adventure", the first in his Fafhrd and the Gray Mouser series.
Unknown was forced to a bimonthly schedule in 1941 by poor sales, and cancelled in 1943 when wartime paper shortages became so acute that Campbell had to choose between turning Astounding into a bimonthly or ending Unknown. The magazine is generally regarded as the finest fantasy fiction magazine ever published, despite the fact that it was not commercially successful, and in the opinion of science fiction historian Mike Ashley it was responsible for the creation of the modern fantasy publishing genre.
Issues of Unknown, showing volume/issue number. John W. Campbell was editor throughout.
In May 1923, the first issue of Weird Tales appeared, from Rural Publications in Chicago. Weird Tales was a pulp magazine that specialized in fantasy stories and material that no other magazine would accept. It was not initially successful, but by the 1930s had established itself and was regularly publishing science fiction (sf) as well as fantasy.Weird Tales was the first magazine to focus solely on fantasy, and it remained the pre-eminent magazine in this field for over a decade. In the meantime, science fiction was starting to form a separately marketed genre, with the appearance in 1926 of Amazing Stories, a pulp magazine edited by Hugo Gernsback. In 1930 pulp publisher Clayton Publications launched Astounding Stories of Super Science, but the company's bankruptcy in 1933 led to the acquisition of the magazine by Street & Smith. The title was shortened to Astounding Stories, and it became the leading magazine in the science fiction field over the next few years under the editorship of F. Orlin Tremaine. At the end of 1937 John W. Campbell took over as editor.
By 1938, Campbell was planning a fantasy companion to Astounding:Weird Tales was still the leader in the fantasy genre, though competitors such as Strange Stories were also being launched. Campbell began acquiring stories suitable for the new magazine, without a definite launch date in mind. When Eric Frank Russell sent him the manuscript of his novel Sinister Barrier, Campbell decided it was time to put his plans into action. The first issue of Unknown appeared in March 1939. It was a monthly at first, but poor sales forced a switch to a bimonthly schedule beginning in February 1941. In December 1940 the subtitle Fantasy Fiction was added, and in October 1941 the main title was changed to Unknown Worlds; both changes were intended to make the genre of the magazine clearer to potential readers. When wartime paper shortages became severe in late 1943, Campbell made the choice to keep Astounding monthly and cancel Unknown, rather than switch the former to a bimonthly schedule as well. The last issue was dated October 1943.