American Science Fiction was born with the first issue of Hugo Gernsback’s AMAZING STORIES in 1926. Science fiction had appeared in other magazines for a number of years prior to that, but AMAZING was the first magazine devoted exclusively to science fiction.
It was a big success, and was followed shortly thereafter by WONDER STORIES, also by Gernsback, and by ASTOUNDING STORIES. Many people date the real beginnings of Science Fiction to the late 1930’s when John Campbell took over editorship of ASTOUNDING. This publication was to become the most influential publication in the industry, perhaps because Campbell insisted on some scientific basis for his stories, even if the science had not yet been invented. He also nurtured a number of the classical writers in the genre, including Asimov, Heinlein, Van Vogt, and L Ron Hubbard.