Dorothy Shepard, Wrigley's Gum Billboard, 1939. Get a closer look in the Online Archive: http://oa.letterformarchive.org/item?workID=lfa_shepard_0087
A photograph of the billboard as it appeared in Fortune magazine. http://oa.letterformarchive.org/item?workID=lfa_shepard_0088&LFAPics=Yes
Old film footage of the sign shows the animated bubbles in action:
Close-up footage of the Wrigley's sign at a later time stamp: