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A British Diplomat Reveals the Origins of the Lewis and Clark Expedition

This letter from English diplomat Edward Thornton to British Secretary of State for Foreign Affairs Lord Hawkesbury reveals the secretive origins of the Lewis and Clark Expedition. Thornton reveals President Jefferson's plans to launch a western expedition "entirely of a scientific nature" and mentions his request that Thornton grant the explorers a passport should the explorers encounter British subjects. Unbeknownst to Thornton, negotiations were already underway with the French to implement the Louisiana Purchase, which would double the size of the territory then held by the United States.

Edward Thornton to Lord Hawkesbury

My Lord, Philadelphia 9th March 1803.

One of the two Acts of Congress, passed in secret sessions of the two Houses, and discussed with closed doors, relates to the encouragement and extension of the external commerce of the United States, and appropriates the sum of two thousand five hundred dollars for that purpose; and it requires some explanation to make Your Lordship aware of the necessity of secrecy on a subject, which has been very often examined before, and which on the face of it does not present any circumstance requiring concealment. The President has for some years past had it in view to set on foot an expedition entirely of a scientific nature for exploring the Western Continent of America by the route of the Great River Missouri, and for tracing the proximity of the sources of this river to the streams, which fall on the other side into the Pacific Ocean. He supposes this to be the most natural and direct water-communication between the two Oceans, and he is ambitious in his character of a man of letters and of science, of distinguishing his Presidency by a discovery, now the only one left to his enterprize—the Northern Communication having been so ably explored and ascertained by Sir Alexander Mackenzie's journeys. But the constitution of the United States according to the comments of the most able jurists of the country does not permit the general government to offer bounties for the promotion of discoveries or for the advancement of science; and motives of prudence and humanity would equally prevent him from sending persons on an expedition of much peril and not strictly within the limits of legislative authority without apprizing the Congress of the real state of the case. A certain degree of secrecy was absolutely necessary before the commencement at least of the expedition: and it is with this view that the Congress have received the President's communication with closed doors, and have in the same manner authorized an appropriation with the ostensible object of extending the external commerce of the country, but with a complete understanding of the real nature of the plan in contemplation.

This is the state of the case, as the President himself represented it to me a day or two before I left Washington, requesting at the same time, if I felt it consistent with my duty, to furnish the Gentleman, whom he has selected for this enterprize, with a passport, that might secure him as far as related to His Majesty's subjects from groundless suspicions, and that would explain its real object, which is exclusively scientific. He assured me that it was in no shape his wish to encourage commerce with distant or indeed with any Indian tribes, which could only be done by attracting them towards the territory of the Union, or by withdrawing the white inhabitants from their proper business of agriculture, and that the Gentleman entrusted with the conduct of the business would carry no articles of commerce whatever except such as would be indispensably necessary to secure him a favourable reception and passage through the Indian tribes dispersed on the banks of the Missouri.

The Gentleman he has selected for the journey is his Secretary, Captain Merriwether Lewis, a person in the vigour of his age, of a hardy constitution, and already acquainted with the manners of the Indians by his residence in the Western Settlements. He is to be accompanied by a small party of eight or ten boatmen of his own selection, and such Indian hunters as he can prevail upon to accompany him. It did not appear to me that any injurious consequences could arise from granting a passport on the terms and with the views expressed by Mr. Jefferson, and I hope Your Lordship will not think that in paying this mark of personal attention to the President's wishes, I have materially exceeded the limits of my duty.

The apprehended occupation of Louisiana by the French seems to have accelerated the determination of the President, as he thinks it certain that on their arrival they will instantly set on foot enterprizes of a similar nature. I have the honour to be etc.


Source | Donald Jackson, ed., Letters of the Lewis and Clark Expedition, with Related Documents, 1783-1854, (Urban: University of Illinois, 1978), 25-27.
Creator | Edward Thornton
Item Type | Diary/Letter
Cite This document | Edward Thornton, “A British Diplomat Reveals the Origins of the Lewis and Clark Expedition,” SHEC: Resources for Teachers, accessed September 29, 2023,

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