This “Histomap,” created by John B. Sparks, was first printed by Rand McNally in 1931….

This giant, ambitious chart fit neatly with a trend in nonfiction book publishing of the 1920s and 1930s: the “outline,” in which large subjects (the history of the world! every school of philosophy! all of modern physics!) were distilled into a form comprehensible to the most uneducated layman.

The 5-foot-long Histomap was sold for $1 and folded into a green cover, which featured endorsements from historians and reviewers. —Slate.