The Missouri Compromise, by the terms of which slavery<span> was henceforth excluded from the territories north of latitude 36°30' (the southern boundary of Missouri), alarmed Thomas Jefferson, as he told John Holmes in this famous letter, “like a firebell in the night.” The vividness of the image was in keeping with the passions of the time. Despite being a slaveholder himself, Jefferson publicly disapproved of slavery. He even more strongly disapproved of any action on the part of Congress that, in his view, exceeded its constitutional authority. Slavery, Jefferson believed, would die a natural death if left alone; but the very life of the Union depended on maintaining a due measure in legislative acts. In addition, the Missouri Compromise had drawn a line across the country on the basis of a principle, not of geography; such a line, “held up,” as Jefferson put it, “to the angry passions of men,” could have no other ultimate effect than the disastrous rending of the body politic. Holmes, a Massachusetts man, was one of the few Northern congressmen to vote against the Tallmadge Amendment that would have excluded slavery from Missouri itself; Jefferson's prophetic letter to him was written April 22, 1820, just a month after the passage of the Missouri Compromise. </span>
