Even before the United States won its independence from Great Britain, westward expansion was a powerful force among Americans. So strong was the compulsion to seek the new country that the British, fearing loss of control over migrating colonists and war with the Indians, tried to halt the westward movement by decree. The Royal Proclamation of 1763 was predictably unsuccessful. By the time of the Revolution, the westering urge was firmly imbedded in American society.
The newly independent United States offered ample space for its mobile, restless citizens. Bordered by Spanish Florida to the south and British Canada to the north, the nation stretched from the Atlantic Ocean to the Mississippi River. Most settlements were still east of the fall line on the slopes of the Appalachian Mountains. Far from being trackless wilderness, the scantily populated woodlands and river valleys of the interior were laced with trails that linked the yet unconquered native peoples. But to the Anglo-Americans, trans-Appalachia was imperfectly known and indifferently charted.
While pioneers poled flat-bottomed boats down the Ohio River and led oxcarts through the Cumberland Gap, President Thomas Jefferson added another huge domain to the nation. The purchase of Louisianna grew out of Jefferson's desire to obtain the port of New Orleans from France. When the French government expressed its willingness to part with all of Louisiana, Jefferson leaped at the opportunity. The vaguely defined territory, which stretched north and west from New Orleans to Canada and the Rocky Mountains, was fully as large as the United States itself.
Even before completing the negotiations, Jefferson intended to send an exploring party across the Mississippi to the Rockies and beyond, "even to the Western Ocean." The government lacked an agency to administer such an enterprise, a depot for maps and instruments, and a pool of trained explorers versed in surveying, cartography, and topographical drawing. Consequently, Jefferson had to create his expedition out of whole cloth, down to assembling such maps and information on the vast region as then existed. Captain Meriwether Lewis, Jefferson's choice to command the party, underwent an intensive education in scientific observation and collection at the American Philosophical Society's Philadelphia headquarters before setting off with Captain William Clark and a small band of frontiersmen.  Their successful journey of 1804-1806, up the Missouri River and over the mountains with the intrepid Sacajawea as a guide, then down the Columbia River to the Pacific Ocean, was all the more remarkable for their scant training and experience.
Four more expeditions departed for portions of Louisiana during Jefferson's presidency. In 1804 William Hunter and John Dunbar made an abortive attempt to follow the Red River to its source in Spanish Texas, and a year later Spanish soldiers thwarted a similar effort by Thomas Freeman. Lieutenant Zebulon M. Pike ranged far over the new country on explorations of 1805-1806 and 1806-1807. Although he erroneously claimed to have found the source of the Mississippi, he did explore much of the river's upper reaches. On his second journey, he also examined large parts of the Southwest before Spanish forces arrested him and confiscated his papers. Pike won wide acclaim for his exploits, and indeed his efforts were far more significant than those of either Hunter and Dunbar or Freeman. 
All of Jeffersonian expeditions shared important characteristics. Their commanders, although men of intelligence and courage, were novice explorers. Some possessed frontier experience, but none were trained specifically for exploration. Pike, for example, made numerous errors that could be attributed to an inadequate background. His estimate of the altitude of Pike's Peak missed the mark by 4,000 feet, and his reading of a nearby latitude erred by about thirty-five miles.  Moreover, Pike and the other explorers depended primarily on the will and curiosity of one man, President Jefferson, for their support. The government gave them no institutional underpinning.
In the decade after Jefferson's presidency the government established the basis for the professionalization of official exploration. In 1816 topographical officers, known as geographers during the Revolution and as topographical engineers during the War of 1812 and thereafter, were added to the peacetime Army. Unlike the other officers of the Corps of Engineers, whose primarily military duties centered on the construction and maintenance of fortifications, "topogs" performed essentially civil tasks as surveyors, explorers, and cartographers. Two years later the War Department established the Topographical Bureau under Major Isaac Roberdeau to collect and store the maps and reports of topographical operations. Like the topogs, who numbered only six at this early date, the Bureau was placed under the Engineer Department. 
Almost from the outset there was a great demand for the skills of the topographical engineers. The accelerated movement of Americans into the interior of the continent served to emphasize the nation's need for networks of transportation and communication. Congress recognized the compelling nature of the requirement in 1824 by passage of the General Survey Act. This law, which authorized surveys for a national network of internal improvements, became the basis for heavy topog involvement in the development of canals, roads, and later railroads. 
Along with the growing importance of the topogs came increases in their numbers and improvements in the organizational structure. Most of the changes came during the first decade of Colonel John J. Abert's tenure as chief of the Topographical Bureau. A strong-willed and ambitious West Pointer who received the appointment after Roberdeau died in 1829, Abert sought independence for both the Bureau and the topogs. He realized the first goal in 1831, when Congress removed the Bureau from the Engineer Department and gave it departmental status under the Secretary of War. Seven years later he attained the second objective and became chief of an independent Corps of Topographical Engineers, a position he held for twenty-three years. Free of Engineer Department control and consisting of thirty-six officers, the organization of 1838 was a far cry from the handful of topogs in 1816. 
Colonel Abert sought a great deal more for the topogs than prominence within the bureaucracy. While Roberdeau had been content to manage the office as a depot for maps and instruments and as a clearinghouse for correspondence, Abert saw his role as a planner and administrator for national policy regarding internal improvements and western exploration. As a member of the Board of Engineers for Internal Improvements, established to evaluate projects considered under the General Survey Act, Abert had a part in the selection of tasks and their execution.  In western exploration, which for many years took a back seat to internal improvements, Abert's role remained minor. His Bureau distributed instruments, collected maps, and forwarded correspondence.
Individual members of the Corps of Topographical Engineers, however, achieved great importance in western exploration and surveys. During the expansionist era of the 1840's, from the first stirrings of Oregon fever in the early years of the decade to the acquisition of the huge southwestern domain after the Mexican War, topogs examined the new country and reported their findings to a populace eager for information about the lands, native peoples, and resources of the West. Best known of all was John C. Frémont, the dark-eyed and flamboyant Pathfinder who led three parties to the Rockies and beyond during this age of expansion. The ranks also included William H. Emory, author of a perceptive assessment of the Southwest, and James H. Simpson, discoverer of the ruins of the ancient pueblo civilization of New Mexico. Howard Stansbury, whose report of an exploration of the Great Salt Lake is still considered a frontier classic, also wore the gold braid of the Corps of Topographical Engineers. In the 1850's, when the emphasis shifted from reconnaissance to more detailed exploration and roadbuilding, topogs continued to make their marks. John N. Macomb laid out the basic road network of New Mexico, and George H. Derby initiated harbor improvements in California, while Joseph C. Ives became the first Anglo-American to descend the Grand Canyon.
The disparity between the renown of members of Abert's Corps and the obscurity of his Bureau was due to the absence of a government policy regarding exploration. Topographical Engineers frequently went into the new country on an ad hoc basis, at the behest of a politically powerful figure like Missouri Senator Thomas Hart Benton, or to accompany a military expedition. From Major Stephen H. Long's 1819 journey up the Missouri River as a minor adjunct of Colonel Henry Atkinson's Yellowstone Expedition to Emory's southwestern exploration with the Army of the West during the Mexican War, Topog exploration often took a secondary position to other purposes.
When exploration and surveys in the trans-Mississippi West were finally organized and coordinated in the 1850's, Abert no longer wielded the political influence that had brought his ambitions so near fruition in the 1830's. Duties he hoped would devolve on the Topographical Bureau went instead to the Office of Pacific Railroad Explorations and Surveys, created by Abert's political foe, Secretary of War Jefferson Davis.  Consequently, the story of topog explorations and surveys in the West was generally that of individual officers' achievements instead of a Bureau accomplishment. For Colonel Abert, their attainments represented a vision only partly fulfilled.
Despite the lack of a unified policy and central direction, the apparently episodic history of topog expeditions forms a coherent entity. Topographical officers provided the necessary link between the first explorations of the mountainmenthose rude, brawling beaver trappers who first probed far beyond the frontier and were no less than walking storehouses of geographical knowledgeand the civilian scientific specialists who undertook a rigorous study of western natural history and resources after the Civil War. Between the beavermen of the American Fur Company and the sophisticated specialists of the United States Geological Service, topogs provided the nation with an overall picture of the trans-Mississippi region. They explored bits and pieces as opportunity allowed until a coherent general understanding of western topography emerged in the form of Lieutenant Gouverneur K. Warren's map of 1857. His achievement, the first accurate overall depiction of the trans-Mississippi West, was a milestone in American cartography. Thereafter, topog activity centered on filling in the few blank spaces in Warren's map. During the Civil War, the Corps of Topographical Engineers was merged into the Corps of Engineers, whose officers renewed the topogs' efforts after Appomattox. Within a few years, however, civilian scientists took over the work and carried it forward. By then the officer-explorers had done their major task. They had extended and codified the knowledge of the mountainmen and in turn laid the groundwork for scholarly analysis. The Topographical Engineers had performed an essential service to a nation growing in size and in its understanding of itself.
Last Updated: 17-Mar-2005