As described at Fancyclopedia, “The 14 Leaflet was the clubzine for the first iteration of the Chicago Science Fiction League, Chapter 14 of the SFL. Published from November 1935 until Spring of 1937, it ran for at least nine issues and included the writings of Jack Darrow.”
The only online issue seems to be that of Spring, 1937, which has cover art by Walter Dellenback. The illustration having neither name nor description, seems to be a symbolic depiction of a city-scape, futuristic by virtue of the vertically elongated towers and spacecraft descending from upper left. Overall, the cover art seems to have very much of a 1939 New York World’s Fair “City of the Future” vibe. It’s also reminiscent of H.W. Wesso’s interior artwork for the opening page of Manly Wade Wellman’s story “Nuisance Value”, which would appear in the January, 1939 issue of Astounding Science Fiction.
For your further distraction…
The 14 Leaflet, at…
… Internet Speculative Fiction Database
Chicago Science Fiction League, at…
William H. Dellenback, at…