Highlights From The Vault — Colorful World

Throughout history, color has been used on maps for a number of different reasons.

From illustrated artistic works of fantasy to visual depictions of scientific data, the use of color has changed throughout cartographic history. In this From the Vault selection, we’ll explore several creative uses of color and the different ways it can be used to visualize map-based data.

Applied Geographics, Inc., Commonwealth of Massachusetts House legislative districts : (Chapter 273 of the Acts of 1993) (1994)

Perhaps the most frequently-seen use of color on maps is to differentiate self-enforced boundaries created between governments. Political maps, such as this 1994 visualization of legislative districts in the Massachusetts House of Representatives, employ color as a way to visibly separate political entities. As political boundaries became more well-defined throughout history, there was an increasing need for map boundaries to be made more visually distinct.

Willem Janszoon Blaeu, Noua totius terrarum orbis geographica ac hydrographica tabula [1638]

Some early cartographers created maps purely for ornamental purposes, using color to draw attention to important or interesting features. In this particular map, this is evident given how much of the space is reserved for artistic depiction and ornamentation as opposed to navigational features. The border includes illustrations of planets, the four seasons, the seven wonders of the ancient world, and the four classical elements (earth, air, fire, and water). Drawings of monsters and rocking ships helped paint a picture of the perilous conditions explorers might face at sea.

Fred. W. Rose, Angling in troubled waters = der fischfang im truben = la peche en eau trouble = la pesca nelle acque turbes : a serio-comic map of Europe [ca. 1899]

“Serio-comic” maps such as this one became a popular form of political commentary in the late 1800s. The most well-known example was the “octopus map”, depicting the eight-armed Russia grappling with the Ottoman Empire. Rather than displaying navigational or data-based information, the serio-comic mapmaker uses color to allude to national stereotypes and make a political argument. Some common national caricatures are on display in this map, such as the dapper Brit “John Bull” and the use of Napoleon to represent his native Corsica.

Arthur Zaidenberg, Downtown district of Manhattan (1938)

Tourist-centric maps, such as this guide to the 1939 Financial District of New York City, use color to draw the viewer’s eye to particular features. The unconventional color scheme and use of negative space make this an interesting example of promotional cartography. Public green space, busy blue streets, and orange land give way to towering bright white skyscrapers, made all the more visible by the lack of color.

This map communicates a cultural narrative of the founding of “Nieuw Amsterdam” through the portrayal of important historical events and figures. Simultaneously showing sites of historical buildings and the modern skyscrapers which now take their place, the map shows how layered history can be in a city like New York.

Charles Henry Hitchcock, Geological map of the United States (1872)

Commissioned for an atlas of the 1870 census, this map is one of the first geological maps to make use of color when differentiating between geological periods. The immense size of the United States and its vast geographical diversity often requires several different classifications to accurately represent the country.

Geological survey maps such as this one represent years of hard work collecting samples and conducting fieldwork. Researchers can then use these surveys to identify deposits of natural resources and locate areas at risk of natural hazards.

Medical Area Service Corporation (Boston, Mass.), A land ownership map for the Longwood Medical Area as of January 1980 (January 1980)

Maps of dense urban areas, like this map of property holdings in the Longwood Medical Area, frequently rely on color to distinguish dense areas with varied land ownership. This map in particular makes use of both color and shading to portray the complex possession rights in this part of the city.

Commissioned by the Medical Area Service Corporation (MASCO), this map was part of a study with the goal of reducing traffic congestion and increasing transit accessibility. MASCO eventually became the Longwood Collective, an organization providing public services to neighborhood employers and residents.

Density of population in greater Tokyo - census of 1926 [1928]

This map of population density data from Tokyo’s 1926 census shows how poor color choices can influence map readability. At first glance, it appears that there are only 3 or 4 separate color-coded categories, but the key reveals that slightly different shades of the same color represent different levels of density.

Although having fewer colors may make a map appear more "clean", the lack of color differentiation can make the map harder to understand. High-contrast color schemes are a crucial element cartographers consider when ensuring their maps are understandable for generations to come, especially because age and light exposure can fade colors in different ways.

Massachusetts Coastal Zone Management Office, Resources on Georges Bank and Nantucket Shoals [1976]

“Hatching” is a technique sometimes used by cartographers to visually separate categories without the use of color. This technique is a frequent feature of early computer-made maps due to the limitations of representing digital color at that time. Hatching can also provide better visual accessibility to viewers who may perceive color in different ways or not at all.

This 1975 map of the Massachusetts coast combines color, shading, and hatching to show the complex overlap of fish spawning grounds, petroleum availability, and fishing activity.

Shadesets (1986–1991)

One of the ways color was first added to computer-designed maps was through the use of an electrostatic plotter. Cartographers used shadesets like this one to pick out color schemes for their maps, carefully considering elements like contrast, opacity, and accessibility.

Starting in the 1800s, mathematicians debated over how many colors were needed on a map so that no two adjacent regions had the same color. The resulting ‘four color theorem’ was formally proven in 1976, becoming one of the first mathematical problems solved with the use of a computer.