Founded in 1939,
Unknown (later
Unknown Worlds) was an indication of the faith publishers
Street & Smith were ready to place in their young editor of
Astounding,
John W. Campbell, Jr. Despite the rather rocky history of
fantasy fiction pulps, with the failures of largely-fantasy
The Thrill Book and
Astounding's former Clayton stablemate
Strange Tales, along with the continuing marginal commercial status of
Weird Tales, Campbell apparently made the argument that work such as Eric Frank Russell's
Sinister Barrier, the lead novel in the first issue (dated March), would be better presented in a fantasy setting rather than as
science fiction in
Astounding. Considering the thread of fantasy and near fantasy Campbell would continue to publish in
Astounding after
Unknown's folding in 1943, it was clear that his heart was at least as much with the kind of "rational fantasy" he published in
Unknown as with the "hard" science fiction he is best-remembered for.
Sinister Barrier wouldn't've been too out of place in
Astounding, but the first issue also boasted a fine grim
Manly Wade Wellman horror story, "Where Angels Fear," and H. L. Gold's "Trouble with Water," a fresh variation on the kind of humorous fantasy
Thorne Smith was publishing to great succeess in book form. This last vein was probably the mode
Unknown has been best remembered for, stories which followed
H.G. Wells's dictum that a fantastic story should have only one miraculous situation in it, and retain as much realism as possible around that miracle; Campbell published a number of similar works, particularly by
L. Sprague de Camp alone and in collaboration, which featured a fairly rigoruous working-out of the limits of the fantasy devices employed. Rather more straightforward exotic-adventure fantasy, by the likes of
L. Ron Hubbard and
Norvell Page, was also a staple of the magazine, which was the first to publish both
Fritz Leiber and his
sword and sorcery heroes
Fafhrd and the Gray Mouser (stories which Campbell supposedly consistently suggested would be better suited to
Weird Tales, where editor
Farnsworth Wright seemed more interested in Leiber's horror fiction). Leiber's groundbreaking
urban horror story "Smoke Ghost" and first novel
Conjure Wife were among the most important examples of the macabre
Unknown would publish; like Leiber, another new Campbell star,
Theodore Sturgeon was also publishing in
Astounding but seemed at least as much at home in
Unknown, offering among many others such influential horror stories as "It" and "Shottle Bop," and slightly more surreal exercises such as "The Ultimate Egoist" and "Yesterday was Monday." In fact, most of Campbell's favorites in
Astounding, including
Robert Heinlein,
A. E. van Vogt,
Cleve Cartmill,
Henry Kuttner, and others, would also publish in
Unknown. The magazine gave up on cover paintings with the 17th issue, July 1940, opting instead for a rather reserved cover template, with several story titles and their authors listed with a small spot illustration next to each title; the magazine also went at this point from standard
pulp size to
bedsheet size. With the 27th issue, October 1941, the title change to
Unknown Worlds was effected, perhaps in hopes of drawing more science fiction-oriented readers; apparently, sales didn't warrant its continuation during World War II's paper shortages, and it folded with the October, 1943, issue, its 39th. Street and Smith tested the market again in 1948, with an all-reprint special annual entitled
From Unknown Worlds, but did not pursue the project further. Many stories published in the magazine have been very widely reprinted since, and several further anthologies have been drawn from its pages, most influentially D.R. Bensen's
The Unknown and its sequel,
The Unknown Five, which printed for the first time an
Isaac Asimov story that had been in
UW's inventory when it folded.
