Slavery in Missouri.

When Missouri applied for admission to the Union as a state in 1819, slavery was already a way of life there. Even before the United States acquired the Louisiana Territory (including the parts that became Missouri), Spanish and French settlers had owned slaves. As part of the agreement to purchase the territory in 1803, the Jefferson administration promised to safeguard the settlers' human property. By the time the population of Missouri (the name given to the territory encompassing the entire Louisiana Purchase besides the state of Louisiana, admitted to the Union in 1812) reached the sixty thousand people required to apply for citizenship, about ten thousand of those people were slaves. The application for statehood was far from routine: it precipitated an ominous sectional crisis that threatened the unity of the nation.

A Deadlock in Congress.

When Congress received the application, James Tallmadge...