Most of Rudolf Cronau's work is in pencil, some in pen, and there are a few watercolors. Some of his drawings were transferred into collotypes, a photo printing process using gelatin. When Cronau returned to Germany in 1882, he published 50 collotypes in a book about his American visit entitled Wunderland to Wunderland. Cronau's drawings are noted for their detail and precise craftsmanship in the German romantic style of the Royal Academy in Düsseldorf.

Cronau's paintings are in the permanent collections of both the Amon Carter Museum of American Art (Fort Worth, Texas) and Thomas Gilcrease Museum (Tulsa, Oklahoma), while his drawings are in the Brooklyn Museum (New York) and Tucson Museum of Art (Arizona.)