Al Feldstein began working at EC comics, publishers of Weird Science, Weird Fantasy, Tales from the Crypt, The Vault of Horror, and The Haunt of Fear in 1948. Soon he became editor of most of EC’s titles. He typically wrote and illustrated a story in each title and drew many of the covers, a mind-bogglingly prolific output. Eventually he stopped doing the art for stories and stuck with editing, writing, and cover illustrations. According to Wikipedia, from “late 1950 through 1953, he edited and wrote stories for seven EC titles.” I’ve always loved his signature, which features elongated horizontals on the F and the T, and an extended vertical on the N.
After MAD creator Harvey Kurtzman got in a fight with publisher William Gaines over ownership of the comic and left EC in 1956, Gaines put Feldstein in charge of the humor magazine, where he remained as editor until 1985.