Jefferson's Instructions to Lewis and Clark

By editor

Three Forks, Gallatin County, Montana

Thomas Jefferson was a man who liked to be thorough, which is a polite way of saying he was a bit of a control freak. When he commissioned Meriwether Lewis in 1803 to lead an expedition to the Pacific Ocean, he didn’t just hand over a map and say, “Go west and see what’s there.” No, he wrote a letter of instructions that ran to several pages and covered everything from the proper way to take celestial observations to the etiquette of meeting Indian nations to the importance of keeping duplicate records in case one set was lost. Jefferson’s letter was a manual for exploration as much as it was a blueprint for discovery.

The central instruction was this: “The object of your mission is to explore the Missouri River, and such principal stream of it, as, by its course and communication with the waters of the Pacific Ocean, whether the Columbia, Oregon, Colorado or any other river may offer the most direct and practicable water communication across the continent for the purposes of commerce.” This was delivered on July 4th, 1803, which was either a patriotic coincidence or a sign that Jefferson saw the expedition as a great American project.

Now, Jefferson was convinced there was a water route through the continent--a so-called Northwest Passage by river--linking the Missouri River to the Pacific. To be fair, in 1803, the geography of the continent was not well understood. The Rocky Mountains were a rumor, like a bad ghost story told by trappers and traders. The idea that a river might run from the Missouri’s headwaters to the Columbia’s headwaters, separated by only a short portage, was not unreasonable considering the knowledge available. It was a hopeful guess, like betting your life savings on a horse nobody’s seen run.

In reality, there was no such water route. Instead, there was a mountain range stretching roughly 400 miles, rugged and hostile. But Jefferson’s instructions, precise and detailed, were entirely based on geography that did not exist--or at least, existed only in the minds of mapmakers and dreamers.

Lewis and Clark reached the Three Forks of the Missouri in late July 1805 and named its three tributaries--the Jefferson, the Madison, and the Gallatin--after the president himself and two of his cabinet members. They followed the Jefferson River south and west into the mountains, dragging their canoes over gravel bars, scouring for the passage Jefferson had sent them to find. Along the way, they encountered Sacagawea, a young Shoshone woman who recognized the country, and her brother, Chief Cameahwait. With Old Toby, a Shoshone guide who knew the mountain trails, they navigated over the Rockies.

It was not a water route, but it was a route nonetheless. They slogged over the Bitterroot Mountains, crossed the Continental Divide, and eventually reached the Pacific Ocean in November 1805. They returned in 1806, proving the continent was traversable, but not by the waterway Jefferson had imagined.

What Jefferson’s instructions reveal is a lot about the era’s economic and political ambitions. The Louisiana Purchase, completed in 1803 for $15 million, doubled the size of the United States overnight and raised urgent questions about the value and utility of the newly acquired lands. Jefferson’s vision was not just about science; it was about commerce and empire. The idea of a water route that could connect the Mississippi Valley to the Pacific would open a trade corridor rivaling the European powers’ colonial enterprises.

Jefferson wrote to Lewis, “You will take care to procure specimens of the soil, roots, and seeds, of the different plants you find, and to note the different kinds of timber, their qualities and uses. These will be important for the commerce of the Western Country.” Commerce, Jefferson understood, was the engine behind exploration. The fur trade was booming. Merchants and speculators were eyeing routes to Asia. The more accurate the geography, the better the chances to turn the wilderness into a market.

But the expedition’s success hinged less on Jefferson’s instructions and more on the men he chose. Meriwether Lewis was a former army captain, who Jefferson groomed personally. William Clark, his co-leader, was no less capable. Together, they organized a party that included interpreters, hunters, soldiers, and guides. Their records were meticulous, their observations scientific, and yet they were not scientists in the ivory tower sense. They were pragmatists, adapting to the land, negotiating with tribes, and improvising when the facts didn’t match Jefferson’s maps.

One contemporary observer, Captain William Clark’s own brother, noted in a letter after the expedition’s return, “They have discovered a country full of promise and peril, but no water highway as was hoped. The mountains are a vast wall, but they found a way over. If there is commerce to be had, it must be on foot or horseback, not by canoe.”

The irony is thick. Jefferson’s instructions were drafted with the confidence of a man who believed in the power of reason and science. Yet the expedition’s greatest discoveries came from human relationships and local knowledge--Sacagawea’s navigation skills, the Shoshone’s goodwill, and the bravery of the Corps of Discovery. They proved the continent was not an insurmountable barrier but a challenge that required more than just maps and instructions.

The expedition also had consequences that Jefferson probably did not foresee. The detailed records and maps they produced fueled land speculation and the push of settlers westward. Within decades, railroads, mining ventures, and banking institutions would reshape Montana and the broader West. The Northern Pacific Railway, chartered in 1864 and completed to Montana by the early 1880s, followed many of the paths first noted by Lewis and Clark. Mines sprang up in the mountains, towns grew, and the economy shifted from fur trade to timber, agriculture, and industry.

The expedition’s legacy is as mixed as the land it crossed--full of ambition, error, perseverance, and unintended consequences. Jefferson’s instructions were the spark, but the men and the land did the real work. As Jefferson himself wrote in a letter to Congress in 1806, “The expedition… has advanced the useful arts and sciences and extended the knowledge of the geography of our country in a manner more extensive and perfect than any former attempt.”

So next time you stand at the Three Forks of the Missouri, take a moment to think about a man who wanted a river highway to the Pacific and instead got a mountain trail marked by courage, chance meetings, and the stubborn will to find a way through the unknown.

See also

• Jefferson's Instructions to Lewis and Clark at Three Forks, Gallatin County
• Headwaters of the Missouri River at Three Forks, Gallatin County
• Lewis and Clark Reach the Headwaters at Three Forks, Gallatin County