This “Histomap,” created by John B. Sparks, was first printed by Rand McNally in 1931. (The David Rumsey Map Collection hosts a fully zoomable version here.) (Update: Click on the image below to arrive at a bigger version.)
The 5-foot-long Histomap was sold for $1 and folded into a green cover, which featured endorsements from historians and reviewers. The chart was advertised as “clear, vivid, and shorn of elaboration,” while at the same time capable of “holding you enthralled” by presenting:
the actual picture of the march of civilization, from the mud huts of the ancients thru the monarchistic glamor of the middle ages to the living panorama of life in present day America.
The chart emphasizes domination, using color to show how the power of various “peoples” (a quasi-racial understanding of the nature of human groups, quite popular at the time) evolved throughout history.
It’s unclear what the width of the colored streams is meant to indicate. In other words, if the Y axis of the chart clearly represents time, what does the X axis (marked as “relative power of contemporary states, nations, and empires”) represent? What’s the meaning of “power” to the mapmaker? And did Sparks see history as a zero-sum game, in which peoples and nations would vie for shares of finite resources? Given the timing of his enterprise—he made this chart between two world wars and at the beginning of a major depression—this might well have been his thinking.