A new hypothesis from economist Andrew Francis argues that the terror of syphilis was so great among US residents that the sexual revolution of the 1960s simply wasn't possible without getting the dreaded disease under control first. In his view, the development of effective treatments—most notably, penicillin—had a more profound effect on culture than even birth control measures.

This may be hard to grasp at first, since the fear of syphilis has fallen off so dramatically today. But there's an easy way to transport yourself back in time 70 years or so, just before the rise of common antibiotics, to get a sense for life in a world where infectious diseases could prove so much more difficult to control. Thanks to the Work Projects Administration (WPA), a federal initiative in the late 1930s and early 1940s that put hundreds of thousands of American to work on public projects, we have an incredible visual archive of life at the time: 2,000 posters created by government-employed artists.

A surprising number of them relate to syphilis; indeed, it's the largest public health issue addressed by the posters, many of which are now archived at the Library of Congress and available online. The posters are alternately terrifying, paternalistic, comforting, and informative, but they are never uninteresting.

Listing image by Library of Congress/WPA