Mapping the Continent: A Tour of Cartographic History

Suggested Readings:

John Rennie Short, The World Through Maps: A History of Cartography (2003). (accessible overview, beautifully illustrated)

Patricia Seed, The Oxford Map Companion: One Hundred Sources in World History (2014). (brief, lively, engaging, with lots of great illustrations)

David Buisseret, ed., From Sea Charts to Satellite Images: Interpreting North American History through Maps 1990. (accessible scholarly articles on many different ways in which old maps can shed valuable light on different aspects of American history)

Jerry Brotton, A History of the World in 12 Maps (2012). (wide-ranging and though-provoking)

Dava Sobel, Longitude (1995). (a wonderfully engaging brief account of John Harrison's efforts to create a clock capable of keeping accurate time at sea)

William H. Goetzmann, Exploration and Empire: The Explorer and the Scientist in the Winning of the American West (1966). (the classic one-volume account of western exploration and mapmaking)

J. B. Harley, David Woodward, et al., eds, The History of Cartography. Ambitious multi-volume encyclopedic world-wide history of this subject, being edited here at UW-Madison. The first three volumes are available for free download as PDFs from this link: More information is available here:

I. Introductions: Mental Maps

My goal today is to return to this Erwin Raisz map that we've seen before and offer a history of cartography and map-making: the story of how it came to be possible for this immigrant from Hungary, Erwin Raisz, to draw this map by the middle of the 20th century. We often take maps for granted, but after today's lecture I hope it will be harder for you to do so. We'll also be exploring the the history of cartographic representations of North America, to reflect on how those representations shape our own mental maps and how they relate to this course's exploration of "The Making of the American Landscape."

First, I'll urge you to consider: What is on your own mental map of the North American continent?

*Saul Steinberg's "View from 9th Avenue," New Yorker, 3/29/1976

Saul Steinberg's depiction of a New Yorker's view of the world--perhaps the most famous cover in the history of The New Yorker magazine--is an amusing reminder of a key insight that we're exploring in discussion sections this week with our map exercise trying to label Erwin Raisz's outline map. We all carry mental maps in our heads, and the contents of those maps are shaped by our personal autobiography, the place where we live, and, crucially, our moment in history. The places closest to us are usually the ones sharpest on our mental maps.

For now, I want to make one point about this image of Steinberg's relative to what we've observed in our discussion sections over the past couple days: of all the things we asked you to put on your maps in section, probably the features you were least able to label--the ones most absent from your mental maps--were the rivers of the United States. This was true even for truly major rivers of immense historical importance to the making of the American landscape. Most of you got the Mississippi River, but that was about it; not even the St. Lawrence was on most of your mental maps, despite its immense significance to the eastern United States (especially the Great Lakes) and, of course, to Canada.

Because of the historical importance of the following geological features, for this class we'd like you to know the the names of the major rivers of the U.S.:

It's also helpful to think of these in terms of the chief watersheds of the U.S. Notice again, the U.S.-centric bias of the mapmaker here has led to the exclusion of the St. Lawrence, even though it controls the entire Great Lakes watershed:

You might wonder: Why is it that so few Americans today don't include many rivers on their mental maps of the U.S.? Why is it important to know them when studying history and the making of landscape?

You yourselves don't travel by water very much. Most of you grew up in a terrestrial and aerial age: automobile, bus, maybe train, and airplane. Rivers just don't matter so much to you—even though a lot of your material life still travels by water. Movement across oceans remains an important part of your life (e.g., shipping containers from China!), as does the commercial corridor that is the Mississippi.

But notice: our mental maps as people traveling by land and air is, historically speaking, quite a recent development: before the 1850s, your mental map would have included many more rivers because they were by far the most important transportation corridors for people and goods alike.

The vast majority of the maps we are going to look at today focus on oceans, coasts, harbors, the rivers that flow into those harbors, and then, eventually, the rivers that reach back into the interior of the continent. If you want to understand why the major cities of the US are located where they are, you need to understand rivers.

So now...another whirlwind tour, this time through the history of cartography and the technologies of mapmaking. The history of mapmaking is one of the most astonishing achievements of the last several centuries, and this lecture should impart some of that wonder.

(Quickly, you should know that we have an incredible resource at our fingertips:

*UW-Madison History of Cartography Project Begun by David Woodward and J. B. Harley in 1981, this is undoubtedly the greatest scholarly project on the history of mapmaking ever attempted. Harley died in 1991, Woodward in 2004, but project continues to be edited on the 4th floor of Science Hall under the editorship of Matthew Edney of the University of Maine. This lecture draws in part on this UW resource, an encyclopaedic history of mapmaking from all over the world for all of human history. There are links to its websites in the "Suggested Reading" section above.

I. Cartography During the Age of Exploration

Our story starts in the Mediterranean and Europe:

The great originator of geographic knowledge was Claudius Ptolemy (c100-c170). He was a Greco-Egyptian writer, mathematician, astronomer, geographer, astrologer, poet. When we look at Ptolemy's maps, we're looking at the work of a very skilled trigonometrician dealing with the vexing problem of how to represent a spherical planet accurately on the two-dimensional page. It is impossible to do this without distortion, so the dilemmas mapmakers face is how much of which kinds of distortions they will choose to accept. The classic trade-offs involving distortions of shapes, sizes, and angles. Ptolemy was one of the first to tackle these challenges systematically, producing what we would today call a particular projection of the spherical globe onto a two-dimensional surface.

No cartographic representations of Ptolemy's work from the world of antiquity remain, so what we know of Ptolemy comes to us from out of the Arab world, via translations of his work, originally written in Greek, into Arabic from the 9th century. In 1406, Ptolemy's Geography was translated into Latin--the lingua franca of the Renaissance--and thereafter Ptolemy's geographical ideas began to circulate widely in the Mediterranean world, increasingly accompanied by contemporary maps to illustrate them. So when we look at Ptolemaic maps today, we are often looking at 15th-century representations of Ptolemy's original maps.

The history of cartography is generally quite well represented in Wikipedia, which often includes open-source versions of the maps I discuss in this lecture. For Ptolemy, see: David Rumsey's wonderful online collection also often includes excellent reproductions of many of these maps:

*Martellus Map, 1491

This map was almost certainly the basis for Christopher Columbus's geographical understanding of the voyage he was about to undertake in 1492: closely dependent on Ptolemy's Mediterranean geography combined with knowledge extending toward the Indian Ocean and China. This map (and Ptolemy's underestimation of the dimensions of the globe) led Columbus to believe that there must surely be a shorter oversea route if one sailed west, rather than overland via the Silk Road or oversea around the Cape of Good Hope at the southern tip of Africa.

*Carta del Cantino, 1502 (first to show America on world map projection)

Columbus never actually realized that he had encountered large land masses, i.e. whole new continents; he simply thought he had reached the outer edges of the Indies. The Portuguese, particularly as reflected in the Carta de Cantino map from 1502 were the first to understand that what today we'd call the Brazilian coast was the landmass they were exploring, and that it was part of a massive unexplored continent. What's important for us today is that this map in 1502 is the first map to show a Continental North America, rather than a map showing—as Columbus believed—that the islands of the Caribbean islands were islands on the eastern edges of Asia.

*Martin Waldseemüller World Map, 1507üller_map

This map from Holland in 1507 is by far the most detailed world map that had been published up until that time, combining Ptolemeic cartography with Portugeuse understandings of the Brazilian and African coasts. This was the first map to show North and South American as named and separate continents, naming them in honor of the Italian explorer and cartographer Amerigo Vespucci ( It represents the height of knowledge as the early 16th-century produced it.

II. Critical Advances in Cartography, Navigation, and Timekeeping

From this point on, we could trace ever-elaborating story of accumulating geographical knowledge, navigational techniques, printing technologies, and popular reception of that knowledge. I won't try to recount the myriad new maps that were created using revised knowledge from various voyages and explorations from the early 16th century forward. Instead, I'll focus on a few highlights—"greatest hits" maps—as well as technical innovations in navigation and mapmaking. I'm going to show you some crucial maps, some crucial cartographic and navigational techniques, and I'm going to try to periodize the gradual increase of knowledge about various geographical knowledge relating to North America. These cartographic and navigational techniques include the following: (a) Latitudinal lines; (b) Projection; (c) "Longitudinal lines" (including their role in changing our understanding of time.

One story is the story of expeditions: This story is told in the Girolamo Verrazzano Map of 1529 (, a trip chartered by King Francis of France. Giovanni de Verrazzano (Girolamo's older brother) made landfall at Cape Fear in North Carolina and, hoping to avoid the Spanish (who had already established a colonial settlement at Saint Augustine in Florida), he sailed north along the coast as far as Nova Scotia, possibly Newfoundland, then sailed back to France. In 1529, Verrazzano's younger brother Girolamo prepared ink on parchment map of discoveries for Pope Clement VII. This is the very first map in world history to represent what would come to be known as New York Harbor...just one example of accumulating new information.

A. Latitude: The Pedro Reinel 1504 Map

This 1504 map by the Portuguese cartographer Pedro Reinel was the first map to depict latitude, an example of technical innovation. For the first time on this chart of Europe and Africa (with a sketchy landmass to the west), Reynal included a scale of latitudes to show angular distance between the equator and the poles. Latitude could be measured on board ship by measuring the angle between the horizon and the North Star (Polaris). Latitudes were crucial for long-distance oceanic navigation, especially since until the 18th century there was no reliable way to keep track of longitudes. (If you're interested in a nice do-it-yourself explanation of how to use the sun or North Star to determine your latitude, here's an easy tutorial:; there are many others readily available on the Web.)

Longitude, in contrast to latitude, is far more difficult to specify and measure: longitudinal lines are not parallel to each other and, more crucially, the globe is spinning. This means that knowing where you are longitudinally is very hard. It was not uncommon for trans-Atlantic sailors to diverge from the intended course by tens or hundreds of miles, which could lead to disastrous results (including shipwrecks) if they found themselves in dangerously unfamiliar waters. Longitude would remain one of the biggest challenges of trans-oceanic travel for more than two centuries after Columbus. We'll return to this point later in lecture.

One attempt to create more accurate navigational maps come to us again from the Mediterranean world: portolans. By the early 15th century, portolans gave very sophisticated representations of coasts, even though formal mapmakers attempting to depict larger land masses (including the makers of world maps) often ignored these working maps. Portolans were practical charts for navigation.

B. Projection: The Mercator Map of 1569

In addition to the innovation of latitudinal lines, creating maps requires solving the mathematical problem of projection: depicting a round globe on the two-dimensional surface of the page. Arguably the greatest cartographer after Ptolemy was Gerardus Mercator, 1512-1594, who helped produce a very particular solution the projection problem aimed especially at the needs of navigators: the Mercator projection. Mercator produced large wall maps, but later in life published a series of smaller regional maps suitable for binding into a bound volume to which Mercator for the first time applied the word "atlas." A large part of his income also came from the sale of globes, astrolabes, and other scientific instruments. In 1569 he published this incredible map, which was only possible via the collection of geographic knowledge via his correspondence with informants all over Europe in six different languages.

Some points to notice in the Mercator Map of 1569:

  • Most of what you can see are representations of the coast; interiors of continents are largely empty except for their depiction of rivers.
  • The most innovative and influential feature of this map is its mathematical solution for how to project a sphere onto a two-dimensional piece of paper. On this map, the projection forces lines of longitude to be parallel (when in fact they converge on each other as they approach the poles). By representing them as parallel lines, Mercator created large distortions of high-latitude land masses, so that Greenland much larger than the continent of Africa--even though Africa is in fact 14 times larger than Greenland..

*Mercator Projection (USGS) *Gall-Peters Projection (USGS)–Peters_projection

The Mercator projection is today widely criticized for its massive distortions of size in the higher latitudes. It has been argued that its distortions have reinforced European imperialism by making Europe, the United States, and what is today often called "the Global North" appear much larger than the "Global South" so that European nations appear larger than their colonial subjects. This projection was critiqued most famously in Arno Peter's 1967 "Peters projection" map, which sought to represent sizes with strict accuracy (more accurately called the Gall-Peters projection because it was first proposed in 1855 by Scottish clergyman James Gall).

Arno Peters vigorously promoted this map from the early 1970s forward as politically less objectionable than any other projection. (Professional cartographers tended to resist Peters' claims, arguing that his distortions were as objectionable in their way as Mercator's.)

To experience the size distortions of the Mercator projection for yourself, you can use this playful website to move different countries to new locations to see their relative sizes in different parts of the map:

*Robinson Projection (USGS) UW-Madison's Arthur Robinson, one of the leading cartographers of the mid-twentieth century, developed a compromise projection in 1963 that was for many years officially adopted by the National Geographic Society, though they eventually chose a different projection in 1998. There is, of course, no perfect projection, since any effort to depict a spherical surface in two dimensions must inevitably generate some combination of distortions in size, angle, or shape.

For our purposes, though, these late twentieth-century debates may distract us from the most important historical question: why would Mercator think it reasonable to create such a distorted representation of the world in the middle of the 16th century? It's all too easy to forget the historical context within which he was working, and the audience he was trying to serve with his new map. To imagine that the Mercator projection is uniquely awful and colonial is to forget the history of why it was invented, which was to help navigators on ships at sea. For that purpose, it remains unsurpassed, and continues to be used by all sailors and navies to this day.

Why? Because a unique attribute of the Mercator projection is that a navigational "rhumb line"--the path a ship follows when it sails on a constant bearing--will appear as a straight line. On any other projection, such a line will appear to curve, making it much harder for navigators to calculate their course. On a Mercator map, they can chart their bearings using a compass and a straight edge, techniques that are used at sea to this day.

In fact, the Mercator projection remains the official projection of the US Navy. Moreover, if you zoom back to global scale on Google Maps or any other web-based mapping service, you will discover that Mercator is the default projection for web-based maps as well. This is because the main users of such programs are people seeking routes and directions toward their intended destinations, and they have the same intuitive expectations about routes of travel that navigators do. When they travel from New York to Los Angeles, they imagine themselves traveling a straight line despite the curving surface of the Earth. The Mercator is not nearly so obsolete as some people imagine!

Let's move to maps of the North American continent:

*Samuel de Champlain, 1574-1635

Samuel de Champlain, who founded New France in 1608, made extensive explorations starting in 1603, producing important maps especially of New England and Canadian coasts. Notice the hazy knowledge of the Great Lakes and the extensive knowledge of the coasts.

*Joliet's Map from 1673 shows us the importance of the Fox River and the area we today call Portage, Wisconsin.

Note that these maps still had not solved the longitude problem, i.e. the problem of how to know where one was in relation to longitudinal lines on the globe.

*C. John Harrison and the Problem of Longitude

The next great innovation solved the immense navigational challenge of longitude, far harder than latitude (which in northern hemisphere could be measured even on board ship by measuring angle between horizon and the North Star). To determine your east-west position, one needed to compare time on board ship (measured by when sun was at height at noon or by position of stars) with time at a fixed reference point...but that required a clock that could keep time accurately despite the changes in temperature, pressure, humidity, and movements experienced on board a ship at sea. This proved a nightmarishly difficult challenge and took centuries to solve, and was so important that the English Parliament passed the Longitude Act of 1714, offering a prize of £10-20,000 (perhaps $2 million in today's money) to anyone who could solve this it. (There is an excellent brief summary in Wikipedia of the challenges and many solutions proposed for calculating longitude:

The person who finally did so--the story is wonderfully told in Dava Sobel's classic book Longitude (1995)--was an English watchmaker named John Harrison. Over several decades, Harrison produced series of ever more precise and accurate timekeepers, until finally his H4 watch (1761) lost only 3 seconds per day even at sea, more accurate than any prior clock in history. Longitude could now be measured precisely anywhere on earth, revolutionizing not just navigation, but mapmaking as well.

How could a clock solve the navigational problem of calculating one's east-west position on the open sea?

You can locate yourself by looking at the stars, looking at the sky, and you can find out where you are relative to the constellations. If you can compare what the sky looks like at that time versus what the sky should look like at a given time at a fixed base point, then you can know your location east-west; but you need to know the time at your reference point. When you know the difference, you know your line of longitude. Calculating both longitude and latitude means you can know exactly where you are even in mid-ocean many hundreds of miles from land.

*Greenwich Royal Observatory and the establishment of the Prime Meridian Marker

The Prime Meridian was established at the Royal Observatory in Greenwich, downstream from London, in 1851, and adopted as the international standard for longitude at the International Meridian Conference of 1884--though France resisted and continued to use Paris as its central meridian until 1911. Greenwich Mean Time (GMT) was established as international time standard in the same negotiations. This means that starting in 1884, the idea of a universal sense of time began to be consolidated in a new way.

III. Mapping North America

We can track evolving understandings of the North American continent by looking at how past cartographers and explorers represented their knowledge of maps:

*Mitchell Map of 1755

John Mitchell's map of 1755 was almost certainly the most influential map of North America in second half of 18th century. It was used in negotiating the Treaty of Paris that ended the American Revolution, influencing the boundaries that were chosen for the new nation in that negotiation. Once again, in a fur-trading landscape, notice that rivers (and coasts) are still the primary focus of this map.

*César-François Cassini de Thury, 1714-1784

The emergence of the modern state in this period, as well as a series of technological innovations, begins to yield maps with interior content that is more than just rivers-focused. This begins to be the great era of national mapmaking: detailed terrestrial maps become military necessities in a Napoleonic landscape.

*Thomas Jefferson, 1743-1826, Louisiana Purchase 1803

Jefferson purchased Louisiana Territory in 1803. Jefferson commissioned two army officers--William Clark and Merriwether Lewis--to survey these new lands and to seek an overland route to the Pacific Ocean at the same time, up the Missouri River, through Montana and Idaho, and down the Columbia River to its mouth. The result of their two-and-a-half year trip was an immense accumulation of geographical knowledge that was eventually compiled on William Clark's famous map of 1810, the most accurate map of the trans-Mississippi West for the next several decades

*William Clark Map, 1810

Once again, notice Clark's focus on rivers. When this map was eventually published in 1814, it showed a radical increase in knowledge of the extent of the continent.

*Thomas Jefferson Establishes United States Coast Survey, 1807

Mapmaking was not just the effort of individual explorers commissioned by federal agencies. One of the first scientific agencies created to map the U.S. was the United States Coast Survey, created by Thomas Jefferson in 1807. The great achievement of the survey under Ferdinand Rudolf Hassler's leadership was the New York Harbor Chart (1845) (note: "chart" denoting survey of coastal bodies, vs. "map" denoting surveys of land). The land-focused analog to the United States Coast Survey was U.S. Army's Corps of Topographical Engineers, established in 1838.

*Clarence King, 1842-1901, 40th Parallel Survey Map (Goetzmann), First Head of USGS, 1879-81

*John Wesley Powell, 1834-1902, Second USGS Director, 1881-94

The interior West of the United States began to be mapped seriously in a series of expeditions too numerous for us to recount in detail in this course. Among the most important were

  • the Pacific Railroad Surveys of 1853-55, seeking to identify alternative routes for a transcontinental railroad
  • Clarence King's 40th Parallel Survey, 1867-72
  • John Wesley Powell's expedition down the Green and Colorado Rivers (though the Grand Canyon), May 24-August 30, 1869.

Clarence King would become the first director of the new United States Geological Survey (USGS) in 1879, and Powell would succeed him in that role in 1881. It remains remains the great mapmaking agency for the terrestrial United States; the Coastal and Geodetic Survey still produces sea charts.