A 1936 poster, designed by Gert Sellheim, one of 58 pieces displayed in “Art Deco: Commercializing the Avant-Garde,” opening Sept. 28 at Poster House in Manhattan.

Art Deco may be hard to define, but you know it when you see it. Its architecture is at once angular—associated with shapes such as chevrons and triangles—and arcs.

The Art Deco building was designed by William Manley King andbuilt in 1939by the Works Progress Administration to serve as a training center for soldiers and National Guardsmen.