In 1820 the Missouri controversy erupted over the issue of slavery in the newly acquired lands of the Louisiana Purchase. It fell to Jesse Burgess Thomas (1777-1853), a junior U.S. senator from the new state of Illinois, to handle the delicate negotiations that led to the Missouri Compromise. Thomas's maturity, good judgment, and restraint helped pull the country back from the brink of disunion and created a compromise that held for thirty-four years. In Dividing the Union, Matthew W. Hall examines the legal issues underlying the controversy and the legislative history of the Missouri Compromise while focusing on the aspects of Thomas's life and character that gave him such influence. The first in-depth biography of Thomas, Hall's work demonstrates how the legislative battle over the Compromise reflected the underlying nuances of the larger struggle over slavery. The text of the Missouri Compromise originated from the Northwest Ordinance.^ Article VI of the Ordinance purported to prohibit slavery in the Northwest Territory, but paradoxically, a provision that assured property rights in another article was used to protect slavery. People in some parts of the Northwest sought to circumvent Article VI by formulating indenture laws and various state constitutional provisions addressing slavery. Pro- and antislavery activists eventually developed quite different interpretations of the relevant language in these documents, making negotiations over slavery in the new territory extremely complicated. As Hall demonstrates, Thomas was perfectly situated geographically, politically, and ideologically to navigate the Missouri controversy. He was the first speaker of the Indiana Territorial General Assembly, one of the first territorial judges in the Illinois Territory, and the president of the Illinois State Constitutional Convention in 1818.^ Because the drive for statehood in Illinois was strong, the convention managed to skirt the divisive issue of slavery, due in large part to Thomas's efforts. That he was never required to clearly articulate his own views on slavery allowed Thomas to maintain a degree of neutrality, and his varied political career gave him the experience necessary to craft a compromise. Thomas's final version of the Compromise included shrewdly worded ambiguities that supported opposing interests in the matter of slavery. These ambiguities secured the passage of the Compromise and its endurance until the Kansas-Nebraska Act of 1854. By weaving Thomas's life story into the history of the Missouri Compromise, Hall offers new insight into both a pivotal piece of legislation and an important, previously overlooked figure in nineteenth-century American politics. -- Inside jacket flaps.