Lincoln kept on hammering away at Douglas’ claim that the public wanted the Missouri Compromise gone. If Lincoln could point to all the ways the political establishment accepted the Missouri Compromise and treated it as a natural default position in the late 1840s, Douglas could switch principles and tell another story.
Senator Douglas sometimes says the Missouri line itself was, in principle, only an extension of the line of the ordinance of ’87—that is to say, an extension of the Ohio river.
Douglas could tell some whoppers. This one sounds almost plausible, since the line of the Ohio and the Missouri Compromise line purported to do the same thing: split off lands reserved to slavery from those reserved to free labor. Furthermore it had the appeal of turning the antislavery movement’s favorite law, the Northwest Ordinance, back on them. They used Jefferson’s slavery ban language in the Wilmot Proviso. They hailed it as the beginning of their movement. They pointed to each repetition of it in territorial law as another strike against slavery and another sign that the nation, as a whole, once thought slavery should someday end and before that be contained.
As an old riverboat man, Lincoln knew his geography. More than that, Lincoln held a patent on a method for lifting riverboats over sandbars, shoals, and other obstructions. You can read it here, if you can handle the poor OCR. He got the idea after a boat caught a snag and stuck with him on it. Flatboats took him twice to New Orleans, where he got to see the heart of slavery up close and personal.Lincoln had been down the rivers too often to miss the absurdity:
I think this is weak enough on its face. I will remark, however that, as a glance at the map will show, the Missouri line is a long way farther South than the Ohio; and that if our Senator, in proposing his extension, had stuck to the principle of jogging southward, perhaps it might not have been voted down so readily.
Mark Twain could move a plantation six hundred miles south for the convenience of fiction, but Stephen Douglas would not haul the Ohio down from where it joined the Mississippi north of Missouri’s southern border.
Lincoln did, however, grant Douglas half a point. If he really meant to extend a line from the Ohio, then the angle the river flowed at would reserve most of the continental United States to freedom. Few antislavery men would have passed up a deal that gave them probably more than even the Wilmot Proviso would.