Cotton promoted slavery
But during the next generation, the south was converted into a section which for the most part was united behind the institution of slavery. This change came about for various reasons. The spirit of philosophical liberalism which flamed high in Revolutionary days gradually became weaker, and a general antagonism between puritanical New England and the slave-holding south became evident. Above all, certain new economic factors made slavery far more profitable than it had been before 1790.
One element in the economic change was the rise of a great cotton-growing industry in the south. Several causes were responsible for this change. Improved types of cotton with better fibers were introduced. Eli Whitney's epochal invention, in 1793, of the "gin" for cleaning the seeds from cotton greatly accelerated production. At the same time, the demand for raw cotton was vastly spurred by the Industrial Revolution which made textile manufacture a large-scale industry. And the opening of new lands in the west after 1812 greatly expanded the area available for cotton cultivation
Cotton culture moved westward rapidly from the tidewater states, spreading through much of the lower south to the Mississippi River and eventually on to Texas. Another factor which placed slavery on a new basis was sugar growing. The rich, hot lands of southeastern Louisiana proved ideal for growing a profitable sugar cane crop in the late eighteenth century, and by 1830 the state was supplying the nation with about half its sugar supply. This required slaves who were brought from the eastern seaboard. Finally, tobacco culture also spread westward taking slavery with it. Therefore the slaves of the upper south were largely drained off to the lower south and west.
As the free society of the north and the slave society of the south spread westward, it seemed politically expedient to maintain a rough equality between the new states then being established. In 1818, when Illinois was admitted to the Union, ten states permitted slavery and eleven free states prohibited it. When Alabama was admitted as a slave state the balance was restored. Many northerners at once rallied to oppose the entry of Missouri except as a free state, and a storm of protest swept the country. For a time, Congress was at a deadlock. Under the pacific leadership of Henry Clay, however, a compromise was arranged. Missouri was admitted as a slave state, but at the same time Maine came in as a free state, and Congress decreed that slavery should be forever excluded from the territory acquired by the Louisiana Purchase north of Missouri's southern boundary. This proved a temporary solution. Jefferson felt that the fire bell in the night had been hushed but for the moment. "This is a reprieve only," he wrote, "not a final sentence. A geographic line, coinciding with a marked principle, moral and political, once conceived and held up to the angry passion of men, will never be obliterated; and every new irritation will mark it deeper and deeper."
Save for a migration into Texas beyond the bounds of the United States, the westward march of the agricultural frontier did not pass Missouri until after 1840. In the meantime, the far west became a field of great activity in the fur trade which was to have a significance in history far beyond the value of the skins which were collected. As in the first days of French exploration in the Mississippi Valley-indeed, as in the first steps of the English and Dutch westward from the Atlantic Coast-the trader was the pathfinder for the settlers. The French and Scotch-Irish "trappers" explored the great rivers and their tributaries and found all the passes of the Rockies and the Sierra Mountains. Through the knowledge they gained of the geography of the western regions, the traders made possible the overland migrations of the forties and the later occupation of the interior. In addition to expanding by westward emigration, the United States in 1819, in return for assuming the claims of American citizens to the amount of $5,000,000, obtained from Spain both Florida and Spain's rights to the Oregon country in the far west.