It achieved its greatest success under editor Frederik Pohl, winning the Hugo Award for best professional magazine three years running from 1966 to 1968.

The most prominent writer to make his first sale to If was Larry Niven, whose story "The Coldest Place" appeared in the December 1964 issue.

By the end of the 1930s, the field was undergoing its first boom,[1] but World War II and its attendant paper shortages led to the demise of several titles.

If's origins can be traced to 1948 and 1949, when Raymond Palmer founded two magazines while working at Ziff-Davis in Chicago: Fate and Other Worlds.

When Ziff-Davis moved to New York City in late 1950, Paul W. Fairman, a prolific writer, went with them, and was soon in touch with Quinn, who decided to found a pair of magazines modelled after Palmer's.

[4] The first issue of If was dated March 1952, with Fairman as editor; it featured stories by Richard Shaver, Raymond Palmer, and Howard Browne, all writers who were regulars of the Ziff-Davis magazines.

Quinn brought in Ed Valigursky as the art editor; he designed striking covers, including some wraparound artwork—an unusual feature—which helped improve circulation.

[4][5] Shaw joined in May 1953 as associate editor and soon began writing editorials (beginning with the September 1953 issue) and assisting with story selection.

Entries came in from writers who were later to become well known, including Harlan Ellison, Roger Zelazny, and Andrew J. Offutt, whose story "And Gone Tomorrow", about a man unexpectedly sent a hundred years into the future, won first prize and appeared in the December 1954 issue of If.

Circulation failed to increase, though this was at least partly due to the problems with distribution, and by early 1959, Quinn decided to sell the magazine.

In the judgement of science fiction historian Mike Ashley, the effect was that If became the weaker of the two magazines, printing stories that were of lower quality than those Gold selected for Galaxy.

"[17] In April 1963, Galaxy Publishing brought out the first issue of Worlds of Tomorrow, another science fiction magazine, also edited by Pohl.

However, in March 1969, Robert Guinn sold all four of his magazines, including Galaxy and If, to Arnold Abramson at Universal Publishing and Distribution Corporation (UPD).

Pohl was in Rio de Janeiro when he heard the news, and decided to resign his position as editor rather than continue under the new management.

[27] The first issue featured cover art by Bob Eggleton, with reprinted fiction by Silverberg and David Brin among other notables.

[13][29] Browne was the editor of Ziff-Davis's Amazing Science Fiction, a leading magazine of the time, and had given Fairman his start in the field in the late 1940s.

[29] Fairman was familiar with Ziff-Davis's stable of writers, and his preference for them was a reflection of his experience, though this did not necessarily serve the magazine well—he referred to the acquisition of Browne's story as "the scoop of the century" and spoke in glowing terms of him in an introductory note despite the fact that Browne was reputed to detest science fiction.

[13] After Quinn dismissed Fairman and engaged Larry Shaw, the magazine improved significantly, and published several well-received stories, including James Blish's "A Case of Conscience" in the September 1953 issue, later to become the first part of Blish's Hugo Award-winning novel of the same name, about a Jesuit priest on a planet of aliens who have no religion but appear free of sin.

Another coup was the serialization of three novels by Robert A. Heinlein, including the award-winning The Moon Is a Harsh Mistress, which ran in five parts from December 1965 to April 1966.

Several of the writers featured in the If-first series, which were published from 1962 through 1965, became well-known, including Alexei Panshin; the most prominent was Larry Niven, whose first story, "The Coldest Place", appeared in December 1964.

Technically this was not Wolfe's first sale, as he had already had "The Dead Man" published in the October 1965 issue of Sir!, but "Mountains Like Mice" had been written earlier.

[42] If's covers during the 1960s were typically action-oriented, showing monsters and aliens; and several of the stories Pohl published were directed at a younger audience.

[13][43] Ashley has suggested that If was attempting to acquire readership from the many new fans of science fiction who had been introduced to the genre through television, in particular via the popular 1960s shows Doctor Who and Star Trek.

[13][25] With the April 1972 issue, UPD began using card stock for the covers, rather than paper, and continued to do so until the magazine ceased publication.

[25][50][51][52] In addition, two anthologies drew all their contents from If without mentioning the magazine: The 6 Fingers of Time and 5 Other Science Fiction Novelets (1965) and The Frozen Planet and Other Stories (1966).