FACING PAGE This map is a population density surface derived from the 2020 US Census. The clear delineation of human settlement patterns in the middle of the country is the edge of the 30-inch annual rainfall zone—to the east you do not need to irrigate crops; to the west you must. The linear features that look like strands of beads correspond to settlements along the earliest railroads, historically given a lot of land during the homesteading years. Laws governing the railroads required a town to be built along the track every 100 miles. “Maps by their nature are systematic. That system is now driven by computers, part of a technological development that we can safely term a revolution. DAVID RUMSEY Map collector, Cartography Associates 16 The Power of Where THE POWER OF MAPS Maps in some form have always supported and extended our innate desire and ability to understand where we are in relation to the natural and built environment. Maps show us where we are, lend order to complex environments, and put our surroundings into context by layering in new information to reveal patterns and trends. Nowadays, we apply digital technology to mapmaking. Like all fields of human endeavor, the digital revolution has transformed cartography—the art and science of drawing maps. Maps are a simple and efficient way to understand and communicate quickly. Looking at a spreadsheet, we see rows and columns of data. Using charts and graphs, we see patterns. But when that same data is presented on a map, we suddenly have locational context for the information. Because most of us are already familiar with geography, we can understand the data much faster and more intuitively when we see it as a map. Maps are a sort of cognitive prosthesis. They extend and amplify human thought and analytical reasoning in three primary ways: Seeing the unseen: Maps show us an invisible world beyond our direct (and limited) sensory perspectives. They are not merely recording the world like a photograph. A map may show the layout of a city seen from above, an animated humidity pattern for the past month, or a predictive model of a disease outbreak. Maps expand our cognitive playground outward so we can better understand our world. Reducing complexity: Maps derive much of their value from reducing the messy and overlapping complexity of reality into something focused and understandable. Maps embody the art and science of data reduction as intentionally abstracted representations of our world. A map of rainfall doesn’t literally draw raindrops; it uses symbols to stand for things, what academics call semiotics. Archiving information: Because humans can hold only so much in their heads at once, maps record information that can be recalled, used later, and disseminated, similar to the way that the invention of writing enabled us to communicate across time and space.
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