Introduction

One of the most commonly used types of maps today are flow maps, which simultaneously depict movement in time, place, and volume on a geographical map, as seen in GPS navigation devices. Flow maps were first introduced in 1837 but only became popularized during the second quarter of the twentieth century. Based on the collection of nineteenth- and twentieth-century European and American atlases in the Library of Congress, this chapter examines the developing popularity of flow maps as a graphical method since the mid-nineteenth century.

Historiography of cartography, like historiographies of other sciences and arts, focuses on the innovators and pioneers of the field. However, despite the obvious importance of these trailblazers, they rarely cause the dissemination and popularization of new techniques. I will start by describing the first cartographers, who invented flow maps independently in the United Kingdom, Belgium, and France. Yet, flow maps became something completely different from what they initially intended to be. The introduction of flow maps in commercial atlases appeared much later, in places that had little to do with those original innovators, and reflected themes that were radically different from those present in the pioneering flow maps. The history discussed here is not a linear one of scientific progress, but rather an erratic history of changing paradigms, with no single scientific milestone to mark the point of change.