June 20, 1803

To Meriwether Lewis esquire, Captain of the 1st Regiment of infantry of the United States of America.

. . . . .

The object of your mission is to explore the Missouri river, & such principal stream of it, as, by it’s course & communication with the waters of the Pacific ocean, may offer the most direct & practicable water communication across this continent, for the purposes of commerce.

Beginning at the mouth of the Missouri, you will take observations of latitude & longitude, at all remarkeable points on the river, & especially at the mouths of rivers, at rapids, at islands & other places & objects distinguished by such natural marks & characters of a durable kind, as that they may with certainty be recognised hereafter. the courses of the river between these points of observation may be supplied by the compass, the log-line & by time, corrected by the observations themselves. the variations of the compass too, in different places, should be noticed.

The interesting points of the portage between the heads of the Missouri & the water offering the best communication with the Pacific ocean, should also be fixed by observation, & the course of that water to the ocean, in the same manner as that of the Missouri.

The commerce which may be carried on with the people inhabiting the line you will pursue, renders a knolege of those people important. you will therefore endeavor to make yourself acquainted, as far as a diligent pursuit of your journey shall admit,

with the names of the nations & their numbers;

the extent & limits of their possessions;

their relations with other tribes or nations;

their language, traditions, monuments;

their ordinary occupations in agriculture, fishing, hunting, war, arts, & the implements for these;

their food, clothing, & domestic accomodations;

the diseases prevalent among them, & the remedies they use;

moral & physical circumstances which distinguish them from the tribes we know;

peculiarities in their laws, customs & dispositions;

and articles of commerce they may need, or furnish, & to what extent.

And, considering the interest which every nation has in extending & strengthening the authority of reason & justice among the people around them, it will be useful to acquire what knolege you can of the state of morality, religion & information among them; as it may better enable those who endeavor to civilize & instruct them, to adapt their measures to the existing notions & practices of those on whom they are to operate.

In all your intercourse with the natives treat them in the most friendly & conciliatory manner which their own conduct will admit; allay all jealousies as to the object of your journey, satisfy them of it’s innocence, make them acquainted with the position, extent, character, peaceable & commercial dispositions of the US. of our wish to be neighborly, friendly & useful to them, & of our dispositions to a commercial intercourse with them; confer with them on the points most convenient as mutual emporiums, & the articles of most desireable interchange for them & us. if a few of their influential chiefs, within practicable distance, wish to visit us, arrange such a visit with them, & furnish them with authority to call on our officers, on their entering the US. to have them conveyed to this place at the public expence.

Other objects worthy of notice will be

the soil & face of the country, it’s growth & vegetable productions, especially those not of the US.

the animals of the country generally, & especially those not known in the US.

the remains & accounts of any which may be deemed rare or extinct;

the mineral productions of every kind: but more particularly metals, limestone, pit-coal, & saltpetre; salines & mineral waters, noting the temperature of the last, & such circumstances as may indicate their character.

Volcanic appearances;

climate as characterized by the thermometer, by the proportion of rainy, cloudy, & clear days, by lightening, hail, snow, ice, by the access & recess of frost, by the winds prevailing at different seasons, the dates at which particular plants put forth their flower, or leaf, time of appearance of particular birds, reptiles or insects.

carry with you some matter of the kine-pox; inform those of them with whom you may be, of it’s efficacy as a preservative from the small pox; and instruct & encourage them in the use of it. this may be especially done wherever you winter.

if a superior force, authorised or not authorised, by a nation, should be arrayed against your further passage, & inflexibly determined to arrest it, you must decline it’s further pursuit, and return. in the loss of yourselves, we should lose also the information you will have acquired. by returning safely with that, you may enable us to renew the essay with better calculated means. to your own discretion therefore must be left the degree of danger you may risk, & the point at which you should decline, only saying we wish you to err on the side of your safety, & to bring back your party safe, even if it be with less information.

should you be of opinion that the return of your party by the way they went will be eminently dangerous, then ship the whole, & return by sea, by the way of Cape Horn, or the Cape of good Hope, as you shall be able. as you will be without money, clothes or provisions, you must endeavor to use the credit of the US. to obtain them; for which purpose open letters of credit shall be furnished you

Given under my hand at the city of Washington this 20th. day of June 1803

Th: Jefferson
Pr. US. of America