I feel like I should have put this post under "Illustration" since Saul Steinberg (1914-1999) created 90 covers and 1,200 drawings for The New Yorker magazine. There is often a blurry line between "art" and "illustration," but his work is so compellingly odd and his vision was so fascinating, that I feel it really exists outside of what is traditionally thought of as "illustration." His doodly style betrays the seriousness of his oeuvre.
I love how wriggling, pulsing geometric shapes live in traditional rooms, or people created from different schools of art coalesce into a family portrait. And his interpretations of various cities or places, although sketchy and surreal, manage to capture the essence by eerily pinpointing certain elements that symbolize those places. But of course his most famous piece is a view of the rest of the world, looking west, as seen from 9th Avenue in New York City.
Top to bottom: Paris; Techniques At A Party; Wyoming; untitled; untitled; Georgetown Cuisine; View Of The World From 9th Avenue