John Mitchell. “A Map of the British and French Dominions in North America with the Roads, Distances, Limits, and Extent of the Settlements.” 1755. The Tracy W. McGregor Library of American History

John Mitchell lived for a time in Virginia, but he immigrated to England in 1746 and remained there until his death in 1768. The president of the Board of Trade and Plantations commissioned Mitchell in 1750 to prepare a map of the British colonies in North America with the objective of strengthening Britain’s territorial claims in the West. Drawing on the archives of the British government, Mitchell produced “A Map of the British and French Dominions in North America with the Roads, Distances, Limits, and Extent of the Settlements” in 1755. True to his instructions, Mitchell extended the boundaries of Virginia, both Carolinas, and Georgia across the Mississippi River.

In its treatment of the West, Mitchell’s map depicts the lower Missouri more accurately than any other map of the time. He correctly shows the northern branch of the Missouri to be the main branch of the river. The information on Mitchell’s map led Meriwether Lewis up the Marias River to determine the northern reaches of the Missouri River basin.

Mitchell’s map is one of the most significant maps in American history. It was the only map used during the peace negotiations between Great Britain and the former American colonies that culminated in the Treaty of Paris. The map helped settle many subsequent treaty negotiations and boundary disputes, the last in 1932. Thomas Jefferson recommended that Nicholas King use Mitchell’s map as he prepared a new map for Lewis.

“A Map of the British and French Dominions in North America” went through twenty-one editions and impressions to 1791. Special Collections owns several editions and impressions of Mitchell’s map, the earliest being a third impression of the first English edition (1755), whose lower-left quadrant is shown here.

John Huske. The Present State of North America, &c. London, 1755. The Tracy W. McGregor Library of American History

John Huske’s book included a smaller version of Mitchell’s map, shown here.

Antoine-Simon Le Page du Pratz. “A Map of Louisiana, with the course of the Missisipi.” In The History of Louisiana, or of the western parts of Virginia and Carolina. London, 1763. The Tracy W. McGregor Library of American History

Antoine-Simon Le Page du Pratz, a French military engineer, came to North America in 1718 and spent fifteen years as a planter in Louisiana. While living in Louisiana, he made a five-month tour of its interior. He later wrote Histoire de la Louisiane (Paris, 1758), which contains the map “Carte de la Louisiane Colonie Française avec le Cours du Fleuve St. Louis.”

This map depicts the lower Mississippi and lower Missouri rivers fairly accurately, although it mistakenly shows the Missouri River flowing from the west unimpeded by any mountains. This representation was consistent with the widely held belief that the source of the Missouri was near the source of the Rio Grande. The map includes Lahontan’s system of rivers and lakes in the North, although it labels the river running westward toward the Pacific the “Beautiful River.” In his book, Le Page du Pratz tells of an Indian who discovered a route to the Pacific Ocean via the Beautiful River. The Indian’s path from the Missouri to the Beautiful River is shown on the map.

“A Map of Louisiana, with the course of the Missisipi” is included in the first English edition of Le Page du Pratz’s book, The History of Louisiana, or of the western parts of Virginia and Carolina (London, 1763). Thomas Jefferson owned this edition of the work and used it as a reference when he prepared his treatise on Louisiana. Meriwether Lewis borrowed the English edition from Benjamin Smith Barton, his botany tutor, and took it on the expedition to the Pacific. Several references to Le Page du Pratz’s work appear in the journals of the expedition.

Jonathan Carver. “A New Map of North America From the Latest Discoveries.” In Travels Through the Interior Parts of North America in the Years 1766, 1767, and 1768. London, 1781. The Tracy W. McGregor Library of American History

Jonathan Carver joined in the efforts of Robert Rogers to find a route to the Pacific Ocean. Rogers, a soldier and adventurer who never traveled to either the Missouri or the upper Mississippi rivers, nonetheless published a book in 1765 describing the Mississippi River and the major rivers that flow into it. In 1766 Rogers sent Carver to map the upper Mississippi basin in preparation for a western expedition. Carver crossed Lake Michigan, traversed the Fox and Wisconsin rivers to the Mississippi, and then traveled up the Minnesota River. He was the first English-speaking explorer to venture west of the upper Mississippi River. After wintering with the Sioux Indians, Carver met the expedition sent by Rogers. When supplies failed to arrive, however, the expedition was abandoned.

In 1769 Carver went to England, where he published an account of his travels, Travels Through the Interior Parts of North America in the Years 1766, 1767, and 1768 (London, 1778). Carver’s book is notable for endorsing the height-of-land theory and anticipating the idea of a continental divide. Carver’s map shows the “Mantons R.,” or the upper Missouri, flowing westward to “Pikes Lake,” which is connected by a dotted line to the “River of the West.” While this route represents a convenient passage to the Northwest, Carver’s book is the first to mention a large mountain range to the south (presumably the Rocky Mountains) that blocks the westward passage and serves as a continental divide.

Carver borrowed extensively from earlier books by Hennepin, Lahontan, and Charlevoix. Some critics doubted the authenticity of Carver’s observations and speculated that his travel journal was actually the work of another explorer. Regardless, Travels sold well and appeared in over thirty editions. Thomas Jefferson owned a 1797 edition.

James Cook. “Chart of the NW Coast of America and NE Coast of Asia explored in the years 1778 and 1779.” In A Voyage to the Pacific Ocean. London, 1784.

James Cook was Britain’s greatest navigator. In 1776 he undertook the last of his three famous voyages; he explored the West coast of North America and tried to locate a passage between the Atlantic and Pacific oceans. On this voyage Cook discovered the Hawaiian Islands and sailed up the coast of North America through the Bering Straits to the Arctic Ocean. He concluded that a usable passage to the Atlantic Ocean did not exist. On his return to the Pacific he was killed by Hawaiian islanders.

Cook’s exploration of the Pacific coast of North America was momentous, though fraught with errors. He missed the mouth of the Columbia River, as well as the Juan de Fuca Strait, a passage into Puget Sound. He also mistook Vancouver Island for the mainland. Despite these oversights, Cook’s third voyage significantly increased knowledge of and interest in the Northwest. His chart of the Pacific coast served as a chief reference source for Nicholas King as he prepared his map of America for the Lewis and Clark Expedition in 1803.

More significantly, Cook’s widely read accounts provided fascinating descriptions of the indigenous peoples in the Pacific Northwest and publicized the brisk trade between the Hudson’s Bay Company and the Indians. Cook’s almost incidental discovery of the sea otter trade—he found that the furs of the region’s abundant sea otters brought enormous profits in markets in China—sparked a race to the Pacific Northwest. Upon the 1783 publication of an unofficial account of Cook’s third voyage and the release of the official account the following year, Britain, France, and the new United States joined Spain and Russia in a contest for control of the Pacific Northwest and the sea otter trade.