Science fiction has become so central to our culture that it can be easy to take it for granted, but its modern form arose at a specific historical moment. During the genre’s golden age, which is conventionally dated from 1939 to 1950, its ideas were refined by a relative handful of authors, editors and artists — and its most immediate impact came through its illustrations. Out of the pulps emerged an entire visual language that relied on striking painted covers to attract newsstand buyers, and while it took years for the stories inside to live up to readers’ dreams, the pictures were often unforgettable from the beginning.

This evolution is clearly visible in the magazine best known as Astounding Science Fiction, the most influential title in the history of the field, and in its sister publication, Unknown, which played much the same role for fantasy. Most of the art was produced by commercial freelancers in New York who collaborated closely with editors. The interior drawings tended to strictly follow the text, but cover artists could let their imaginations run wild. Thanks in large part to their work, science fiction in the midcentury achieved its enduring sense of wonder, and its images from this period may turn out to be the genre’s most lasting contribution to our collective vision of the future.