If magazine

if, subtitled "Worlds of Science Fiction", was launched in March 1952, the creation, apparently, of James L. Quinn of the Quinn Publishing Company, not to be confused with Robert Guinn, who later published both If and its sister pulp Galaxy. (The title "If" had previously been used by Con Perderson in 1948 for an amateur magazine.) At first the cover bore only a distinctive if in oversized lower-case letters, but later the subtitle was added over the logo in such a way as to make it appear that the actual title of the magazine was "Worlds of If". In 1972 Worlds of If was made the official name of the magazine, so that issues after 1972 are sometimes indexed separately. The editoral succession at If seems to have been as follows:

Paul W. Fairman: March 1952 - Sept. 1952
James L. Quinn: Nov 52 - Aug 1958
Damon Knight: Oct 58 - Feb 1959
H.L. Gold: July 1959 - Nov 1961 (Gold was ill for part of this period, and some issues listing him as editor were actually edited by Fred Pohl.)
Frederik Pohl, Jan 1962 - May 1969 (Under Pohl, If won the Hugo award for best professional science fiction magazine three years running: 1966, 1967, and 1968.)
Ejler Jacobsson: Oct 1969 - Jan/Feb 1974
Jim Baen: Mar/Apr 1974 - Dec 1974 (If then ceased publication and was incorporated into Galaxy.)
Clifford R. Hong: Fall (September/November) 1986. This attempt to revive If as a quarterly lasted only one issue.