Richard Scarry (1919-1994) published First Book Ever in 1950. It was revised and republished as (Best) First Book Ever in 1979.
Richard Scarry at Random House Kids.
Theodor Seuss Geisel, Dr. Seuss, (1904-1991) first published And to Think I Saw It on Mulberry Street in 1937. It was 20 years later that The Cat in the Hat made his first appearance (1957).