Prior to the creation of Galaxy Magazine, the field was dominated by Astounding, and the somewhat regimented and puritanical world-view of it's editor, John W. Campbell.
Under the editorial direction of Horace L. Gold, Galaxy presented a wittier, more sophisticated point of view. It is indeed arguable that without Galaxy, we would never have seen such works as Bester's "Demolished Man" or "Stars My Destination".
Asimov's "Caves of Steel" also first appeared in Galaxy, although it's sequel "The Naked Sun" later appeared in Astounding. Such groundbreaking works as "The Space Merchants" (initially titled "Gravy Planet"!?!) by Pohl & Kornbluth first appeared there as did Bradbury's "The Fireman", which was later expanded into the novel "Fahrenheit 451". It goes without saying that the advent of Galaxy, along with it's close association with the radio drama X Minus 1, spurred a revitalization of the field that opened up new areas of exploration with regards to topical content and writing style. The social sciences, not just the physical ones, would have a profound effect on the world of tomorrow, not to mention the psychological ramifications of technology....
It is then, fair to say, that as an editor, H. L. Gold had just as much, if not more, influence on the direction of 20th Century speculative fiction as both John Campbell and Hugo Gernsback.
Here then, are a selection of covers from the early years.