Although science fiction had been published before the 1920s, it did not begin to coalesce into a separately marketed genre until the appearance in 1926 of Amazing Stories, a pulp magazine published by Hugo Gernsback. By the end of the 1930s the field was booming. Standard Magazines, a pulp publishing company owned by Ned Pines, acquired its first science fiction magazine, Thrilling Wonder Stories, from Gernsback in 1936. Mort Weisinger, the editor of Thrilling Wonder, printed an editorial in February 1938 asking readers for suggestions for a companion magazine. Response was positive, and the new magazine, titled Startling Stories, was duly launched, with a first issue (pulp-sized, rather than bedsheet-sized, as many readers had requested), dated January 1939.
Startling was launched on a bimonthly schedule, alternating months with Thrilling Wonder Stories, though in 1940 Thrilling moved to a monthly schedule that lasted for over a year. The first editor was Mort Weisinger, who had been an active fan in the early 1930s and had joined Standard Magazines in 1935, editing Thrilling Wonder from 1936. Weisinger left in 1941 to take a new post as editor of Superman, and was replaced by Oscar J. Friend, who was an established writer of pulp fiction, though his experience was in western fiction rather than sf. During Friend's tenure Startling slipped from bimonthly to quarterly publication. Friend lasted for a little over two years, and was replaced by Sam Merwin, Jr., as of the Winter 1945 issue.
Merwin succeeded in making Startling popular and successful, and the bimonthly schedule was resumed in 1947. At the start of 1952 Startling switched to a monthly schedule; this was unusual in that Startling was notionally junior to Thrilling Wonder, its sister magazine, which remained bimonthly.[note 1] Merwin left shortly before this switch, in order to spend more time on his own writing. He was replaced by Samuel Mines, who had worked with Standard's Western magazines, though he was a science fiction aficionado.