To the Senate and House of Representatives of the United States:
The Choctaws, being indebted to their merchants beyond what could be discharged by the ordinary proceeds of their huntings, and pressed for payment, proposed to the United States to cede lands to the amount of their debts, and designated them in two different portions of their country. These designations, not at all suiting us, were declined. Still urged by their creditors, as well as by their own desire to be liberated from debt, they at length proposed to make a cession which should be to our convenience. By a treaty signed at Pooshapuckanuck on the 16th of November, 1805, they accordingly ceded all their lands south of a line to be run from their and our boundary at the Omochita eastwardly to their boundary with the Creeks, on the ridge between the Tombigbee and Alabama, as is more particularly described in the treaty, containing about 5,000,000 acres, as is supposed, and uniting our possessions there from Adams to Washington County.
The location contemplated in the instructions to the commissioners was on the Mississippi. That in the treaty being entirely different, I was at that time disinclined to its ratification, and I have suffered it to lie unacted on. But progressive difficulties in our foreign relations have brought into view considerations other than those which then prevailed. It is now, perhaps, as interesting to obtain footing for a strong settlement of militia along our southern frontier eastward of the Mississippi as on the west of that river, and more so than higher up the river itself. The consolidation of the Mississippi Territory and the establishment of a barrier of separation between the Indians and our Southern neighbors are also important objects; and the Choctaws and their creditors being still anxious that the sale should be made, I submitted the treaty to the Senate, who have advised and consented to its ratification. I therefore now lay it before both Houses of Congress for the exercise of their constitutional powers as to the means of fulfilling it.
Thomas Jefferson, Special Message Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/202312