In the South, slavery had become less and less useful to farmers as tobacco prices began to fall after the American Revolutionary War. But in 1793, Eli Whitney invented the cotton gin. This made Southern grown cotton highly profitable. Cotton also required large numbers of slaves. Most Southerners, however, did not own slaves. But by 1860 cotton and slavery was the strong link in the Southern economy. Maryland, Kentucky, and Missouri, which had many areas with much stronger cultural and economic ties to the South than the North, were deeply divided.