ABSTRACT
Westward migration in the early 19th century inevitably led to tension between residents of slave and free states. Thirty years after the Missouri Compromise, the issue of slavery's expansion in the West was as contentious as ever. As a result of the victory in the Mexican-American War, the United States acquired the entire Southwest: territory that would become the states of California, Nevada, Utah, New Mexico, and Arizona. Abolitionists like Frederick Douglass had done much to influence public opinion, and many anti-slavery Northerners wanted to bar slavery from spreading into territory won from Mexico. Senator Stephen Douglas proposed repealing the part of the Missouri Compromise that prohibited slavery north of 3630', arguing that 'popular sovereignty'. Almost overnight, people who had never publicly opposed slavery's extension became energized against the Kansas-Nebraska Act. By the time the population of Missouri reached the 60,000 people required to apply for statehood, 16 percent of those people were enslaved African Americans.
