Popular sovereignty was the doctrine that the people of a territory, rather than the United States Congress, should decide whether to permit slavery in the territory before it became a state. The doctrine is also called squatter sovereignty. The theory of popular sovereignty developed during the controversy over slavery that is part of the history of the early United States.
The North, as a whole, opposed extension of slavery into any of the land acquired from Mexico after the Mexican War ended in 1848. The South almost unanimously favored expansion of slavery into this new territory. Many people on both sides found the theory of popular sovereignty a useful solution to the disagreement that relieved Congress of a difficult problem. Lewis Cass probably originated the theory of popular sovereignty. But Stephen A. Douglas was its most prominent advocate. Douglas was the first person to use the term popular sovereignty.
The Kansas-Nebraska Act of 1854 permitted the people of the Kansas and Nebraska territories to decide for or against slavery within their respective borders. The authors of the law took for granted that Nebraska would vote free, and Kansas, slave. But antislavery advocates sent many free-state settlers into Kansas, while many proslavery residents of Missouri crossed into Kansas, sometimes to settle, but often only to vote. The bloodshed that resulted showed that the principle of popular sovereignty would not work. Soon after the American Civil War ended in 1865, slavery was abolished and the theory of popular sovereignty lost its significance.
