February 6, 1932. The issue of The New Yorker with this cover date contained the first published cartoon of Charles Addams. It was about a window washer, but I haven't found a copy of it, so I don't know if it had that morbid sense of humor for which he is known and loved.
Of course, it is that morbid streak that made him a favorite of mystery writers and fans. The Mystery Writers of America gave him a Special Edgar Award. And they probably didn't turn their backs on him.