In 1936, Leslie worked with Hortense Mendel to create Gallery 303. It was intended to showcase new American artists and emigres from Europe who were fleeing Nazi Germany. And in 1965, began a lecture series through the gallery, called the Heritage of Graphic Arts. He also set up a graphic arts salon that leaders of the industry including Ladislav Sutnar, Alvin Lustig and Herbert Bayer could discuss design and talk shop.
