I've come to the conclusion that Jefferson's clearly unconstitutional Lousiana purchase was one of his great miscalculations. It legitimized state-sponsored Western expansion and gave the federal government primacy in the administration of vast tracts of land. Naturally, this is one of his legacies that most everyone thinks is just super.
Nevertheless, Jefferson states that should the inhabitants of the new territory wish to secede form the Union at some poimnt in the future, he was perfectly fine with that(see letter to John C. Breckinridge,Aug. 12, 1803):
"...Besides, if it should become the great interest of those nations to separate from this, if their happiness should depend on it so strongly as to induce them to go through that convulsion, why should the Atlantic States dread it? But especially why should we, their present inhabitants, take side in such a question?...The future inhabitants of the Atlantic & Missipi [sic] States will be our sons. We leave them in distinct but bordering establishments. We think we see their happiness in their union, & we wish it. Events may prove it otherwise; and if they see their interest in separation, why should we take side with our Atlantic rather than our Missipi descendants? It is the elder and the younger son differing. God bless them both, & keep them in union, if it be for their good, but separate them, if it be better."
And again in a letter to To Dr. Joseph Priestley, Jan. 29, 1804
"Whether we remain in one confederacy, or form into Atlantic and Mississippi confederacies, I believe not very important to the happiness of either part. Those of the western confederacy will be as much our children & descendants as those of the eastern, and I feel myself as much identified with that country, in future time, as with this; and did I now foresee a separation at some future day, yet I should feel the duty & the desire to promote the western interests as zealously as the eastern, doing all the good for both portions of our future family which should fall within my power."