But was he top notch back then? He's most well known for "creating" Lisp. And I put that in quotes because he never meant for anyone to implement it on a real machine.
re:was he top notch? By 1955 he was an assistant professor of Mathematics and known in his field. In 1956 he organised the Dartmouth conference where the field of Artificial Intellgence - got its name. He was a peer of Claude Channon, Marvin Minsky and Nathanial Rochester - so yes he was top notch. YC audience knows him for Lisp - but he was known for a lot more in his fields of research.