Library of Congress > Collections with Maps > Louisiana: European Explorations and the Louisiana Purchase

A Question of Boundaries

French and American representatives faced a vexing issue when they met in Paris in April 1803 to negotiate a treaty by which the United States would purchase the province of Louisiana from France. Since most of the territory to be exchanged had never been explored, surveyed, or mapped by any European nation or the United States, the negotiators were unable to include within the treaty any accurate delimitation or precise definition of the boundaries of Louisiana.

Previous treaties transferring ownership of Louisiana between France and Spain never included any boundary delineation. For those reasons, no one knew what the Purchase meant in size, nor did anyone have a realistic conception of how its overall terrain should appear on a map.

All that the representatives knew was that the territory historically had been bordered on the south by the Gulf of Mexico and on the east by the Mississippi River between its mouth and its uncertain headwaters. Undeterred by the prospects of such a limitation, or perhaps inspired by the possibilities it offered, the American representatives agreed, according to the ambiguous language of the treaty of cession, to receive on behalf of the United States "the Colony or Province of Louisiana with the same extent it now has in the hands of Spain and that it had when France possessed it."

The negotiators presumably would have requested the most accurate and comprehensive map of the continent likely to be available in Paris at the time. One such candidate would have been Aaron Arrowsmith's 1802 Map Exhibiting All the New Discoveries in the Interior Parts of North America, which embodied the most modern geographic knowledge of North America prior to Lewis and Clark's expedition. By today's standards, this map leaves much to the imagination, particularly with regard to the vast region known as the Far West. Louisiana is no more than a nebulous entity, its only conspicuous boundary an unspecified segment of the Mississippi River.

At the time of the Purchase, both the United States and France presumed that the territory was made up of the Mississippi River, including the various French settlements along the full-length of its western bank; the Red River Valley as far as the frontier of the Spanish province of Texas; the Missouri River to undetermined limits; the town of New Orleans; and the Isle of Orleans that piece of land bounded on the west by the Mississippi River, on the east by the Gulf of Mexico, and on the north, going from west to east, by Bayou Manchac, Lake Maurepas, Lake Pontchartrain, Lake Borgne, and the Mississippi Sound. More complicated was the small region known as Spanish West Florida, which was claimed by the United States as part of the treaty, a claim later challenged by France and Spain.

Even before Louisiana was acquired by the United States, President Thomas Jefferson began to press American claims farther afield. He asserted that Louisiana embraced all of the lands drained by the western tributaries of the Mississippi, including the far-flung and uncharted headwaters of the Missouri and the area drained by its northernmost tributaries, in addition to the West Florida. Jefferson also planned the first transcontinental expedition prior to the negotiations for Louisiana. Once the new territory became part of the nation, federally sponsored expeditions, guided largely by Jefferson's counsel, set about exploring and surveying it to define and describe Louisiana geographically; to expand the bounds of the territory as far to the Southwest, the West, and the North as far as possible; and to make the region's lands and peoples subject to the authority of the United States. Those efforts produced the first reasonably accurate delineations of the American West and began to give formal shape to the boundaries of the new territory.

The first printed map depicting the topography of the Louisiana Purchase was published in 1804 in an atlas by Aaron Arrowsmith. All of the American maps within the atlas, including the one identified simply as Louisiana, were drawn by the American cartographer and draftsman, Samuel Lewis. Arrowsmith and Lewis based their product upon the best information at hand. Their representation of the upper Mississippi and Missouri basins, for example, was borrowed from a groundbreaking map of the American West drawn in St. Louis in 1795 by French engineer Pierre Antoine Soulard. Louisiana, however, included several readily evident errors and blank spaces, among them being a South Fork of the Platte River which extends far south into present-day New Mexico; the omission of the great Colorado River of the West, still awaiting discovery by the United States; an uncertain source of the Mississippi; the Rocky Mountains portrayed too far to the west and in a single broken chain; and a minimized Columbia River system.

Once federal explorations of the West were underway, it was only a matter of time before their newly uncovered wealth of information found cartographic expression. One of the earliest commercially issued maps to incorporate data from the famed 1804 transcontinental expedition of Meriwether Lewis and William Clark appeared in an atlas issued by Philadelphia publisher Matthew Carey in 1814. The map, also drawn by Samuel Lewis, depicts the Missouri Territory Formerly Louisiana, which was organized in 1812, the year that the first state Louisiana was created out of the Louisiana Purchase area (the Missouri Territory comprised the remaining lands). The "probable north boundary of the Missouri Territory," is at odds with British claims to the Pacific Northwest in fact, the "probable" northern and southern boundaries appearing on Missouri Territory Formerly Louisiana correctly intimate that the United States had assumed years of border disputes with Spain and Great Britain.

Within two decades of the Purchase, official boundaries had been realized either through treaty or annexation. The first major adjustment occurred in 1810, when a revolt in that part of Louisiana known as Spanish West Florida today the Louisiana parishes east of the Mississippi River and of Lake Pontchartrain, led the United States to annex the territory from the Mississippi to the Pearl River.

After 1815 the United States concluded treaties with both Great Britain and Spain. As a result of the treaty with Britain, the 49th parallel from the Lake of the Woods (along the present border of Minnesota and Canada) to the continental divide of the Rocky Mountains was established as the northern boundary of the Louisiana Purchase, and the United States gained territorial rights to the Pacific Coast. Under the terms of the 1821 Adams-Onis Treaty, also known as the Transcontinental Treaty, Spain ceded East Florida an area of Florida extending east of the Appalachicola River to the Atlantic Ocean to the United States. The treaty set the western boundary of Louisiana along the Sabine and Red rivers which separate Texas and Louisiana, then north along the 100th meridian to the Arkansas River which it followed westward to its source in the Rockies, then north to the 42nd north latitude, and on a line then west to the Pacific Ocean. An undated subsequent edition of Missouri Territory Formerly Louisiana by Carey and Lewis, probably published after 1818, has been amended by hand in watercolor to record some of the treaty adjustments.

By 1823, when the last bonds issued in Great Britain and the Netherlands for financing the purchase were paid off with interest by the United States Treasury, the total spent for Louisiana amounted to $23,313,567.73. As if sympathetic to President Jefferson's assertions, the boundaries of Louisiana expanded and adjusted over time until they eventually stretched from the Gulf of Mexico to British America (present-day Canada) and from the Mississippi River to the Rocky Mountains. Today the lands constituting the Louisiana Purchase are estimated to cover between 850,000 to 885,000 square miles. Areas once part of Louisiana form six states in their entirety: Arkansas, Iowa, Missouri, Nebraska, Kansas, and Oklahoma; most of the states of Louisiana, Minnesota, North Dakota, South Dakota, Montana, Wyoming, and Colorado; and sections of New Mexico and Texas. At the time of the Purchase, small segments of the Canadian provinces of Alberta and Saskatchewan also were presumed part of the transaction.

View the complete essay (PDF). (1.8 Mb)

Back to top: Back to Top