Writing to Congress in 1777, George Washington had complained that "the want of accurate maps of the Country" placed him at "a great disadvantage." Treating mapmaking as a public expense, the British government staffed its army with surveyors, whose skills were indispensable to making maps. As a result, the British often had a better knowledge of the American countryside than did Washington's army.

Washington himself was a surveyor, but American surveyors had been employed by land-seeking clients, not governments. This approach to mapping yielded local maps, some of which were biased since the clients had an interest in the outcome. Existing maps of entire colonies were compilations of local maps, subject to the all errors that had crept into local surveys and lacking any common geographic frame of reference.

The accurate mapping of large areas that Washington desired required government funding of many survey parties. A typical survey party included several axemen to clear trees, two chain bearers, two or three staff carriers, an instrument carrier, and the surveyor. Surveyors used several basic instruments, including a table equipped with paper, a compass, a telescope for measuring direction and heights, and an instrument for measuring angles called a theodolite. A surveyor first measured a baseline from one point to another, as marked by the chain bearers. Next he commenced a process known as triangulation by picking a landmark in the distance, like a hilltop, and measuring its angle from the baseline. A staff man might be standing on the hilltop with a flag attached to his staff. Finally, the surveyor employed trigonometry to calculate the length of each side of the triangle, one of which would serve as the next baseline. For every hour spent walking a plot of land, the survey party would spend three hours recording their measurements on paper.

Washington's complaint about inadequate maps led to the appointment of Scottish-born Robert Erskine as surveyor general of the Continental Army and to government funding of his workers. After the war, the Land Ordinance of 1785, which specified that public lands be surveyed and divided into townships six miles square before auction, again led the national government to employ survey parties.

The Land Ordinance applied only to land lying outside any state. The national government did not take responsibility for mapping the states. As late as 1800, no state had paid for a survey of its territory, partly because state governments were short of money and partly because few saw the need. This situation would change over the next two decades.

Jefferson's purchase of Louisiana in 1803 pricked a new popular interest in geography. Mapping the Purchase presented several obstacles. Early explorers had surveyed small portions of it, but the territory's vastness ruled out surveys of the entire Purchase. Spain discouraged even local surveys, lest information about this valuable possession leak out. Jefferson and others had to rely on maps compiled from the accounts of travelers who relied on a mixture of their own observations, hearsay accounts of fur traders, and wishful thinking.

Wishful thinking took the form of the belief, embraced by Jefferson, that the sources of the major North American rivers were near each other. If this were true, it would be possible to find a great water highway linking the Pacific to American settlements on the Mississippi. Such a highway would turn America into a commercial link between the riches of the East--Persian silks, Arabian perfumes, the wealth of China--and Europe. It would also facilitate the export of American agricultural produce.

Eager to ensure the profitability of agriculture, Jefferson warmed to this idea. He knew more about geography than anyone else in the American government, and he collected maps, most of which supported the water-highway theory. For example, one map published in Britain in 1778 showed the major American rivers--

the Mississippi, Missouri, Colorado, and Columbia--all originating in a small pyramid of high land in present-day South Dakota.

By the time Jefferson launched the Lewis and Clark expedition to explore the Louisiana Purchase, better maps were available. Jefferson saw to it that Lewis and Clark carried a recent map by an Englishman, Aaron Arrowsmith. Arrowsmith's map showed the Rocky Mountains, which were often omitted by other maps. But when Lewis and Clark reached the source of the Missouri River in June 1805, they found no sign of the Columbia, whose source the Arrowsmith map portrayed as a stone's throw from the source of the Missouri, just "an immense range of high mountains."

Their expedition established Lewis and Clark as authorities on the West and stimulated the public's and states' interest in geography. During their expedition, Lewis and Clark had benefited from accurate charts of local geography drawn by Indians on the ground with sticks or on hides with charcoal. Settled in St. Louis after the expedition, Clark received a stream of explorers and traders who brought him more information about the geography of the Purchase, enough to enable him to draw a manuscript map of the territory. When finally published in 1814, this map gave ordinary Americans their first picture of what Jefferson had bought in 1803. In 1816 John Melish, drawing on Clark's map and his own travels, published by far the most accurate map yet of the United States.

By enabling ordinary Americans to see the vastness of their nation, Melish's map subtly reinforced their sense that the West rightfully belonged to them, not to the Indians or anyone else. The negotiators of the Transcontinental Treaty of 1819, which gave the United States a claim to part of the Pacific Coast, relied exclusively on the 1818 edition of Melish's map. Melish's example also spurred state legislatures to subsidize the drawing of accurate state maps.

Hiring Melish in 1816, Pennsylvania became the first state to finance construction of a state map based wholly on "actual survey." Melish was delighted. He had been insisting that "every state should have its own map" and that such maps should be state property, "subject to the control of no individual whatever." Taking six years to complete, the project cost Pennsylvania $30,000 and exhausted Melish, who died shortly after the map's publication. But other states were quick to follow Pennsylvania's lead. By the 1820s, calls for the construction of canals connecting western farmers with eastern ports were giving new momentum to the drive for accurate and unbiased maps.