Dividing the Union: Jesse Burgess Thomas and the Making of the Missouri Compromise by Matthew W. Hall (review)

Virtually every book and college course on nineteenth-century American politics mentions Jesse B. Thomas, though he rarely gets more than a single sentence. The Illinois senator’s claim to fame is authoring one piece of the three-part Missouri Compromise of 1820. Matthew W. Hall’s Dividing the Union confirms the centrality of the Missouri Compromise to Thomas’s historical importance, while placing the event in the larger context of Thomas’s colorful life in the Old Northwest.

Little has been written about Thomas’s life, but a large body of literature has examined the Missouri Compromise. Hall, a retired attorney connected to Thomas’s family through marriage, briefly notes the existence of this scholarship in a short essay on sources, but he rarely engages with the existing historiography, relying mainly on the Annals of Congress in addition to Thomas family papers. Nonetheless, his book offers a unique contribution. Beyond the biographical details of Thomas’s life, the most valuable aspect of Dividing the Union is Hall’s close attention to the ambiguous nature of constitutional questions surrounding congressional powers over slavery in the territories and new states.

The Northwest Ordinance of 1787 (reaffirmed in 1789 after the ratification of the Constitution) forbade slavery in certain federal ter ritories. Yet, it was not clear whether these territories could legalize slavery after they became states. Hall shows that Jesse Thomas exploited this ambiguity in different ways at different times. In Indiana during the 1810s, Thomas joined an effort, supported in part by a proslavery faction, to create a separate Illinois Territory. The success of this move effectively ended efforts to revive slavery in Indiana, and when Indiana became a state in 1816, its constitution not only prohibited slavery (as Ohio had in 1803), but also forbade any future amendments legalizing the institution. Thus it was clear that in Indiana the Northwest Ordinance’s ban on slavery would be perpetual even after statehood. But in Illinois, Thomas collaborated with inhabitants who wanted to protect forms of unfree labor and “preserve the possibility of approving slavery in Illinois in the future” via “a revision of the constitution after statehood” (p. 99). In 1818, the ambiguity of Illinois’s constitutional provisions that ostensibly prohibited slavery provoked some opposition in the U.S. Congress but not enough to prevent a grant of statehood. As one of Illinois’s first two senators, Thomas was present the following year during the much larger controversy about the Missouri territory’s request to enter the Union as a state with legalized slavery. The ensuing political crisis led to threats of civil war and disunion along with extended debates about constitutional interpretation.

Although Missouri had never been subject to the Northwest Ordinance, the constitutional ambiguities of the ordinance’s slavery ban had implications for it. Northerners, who tended to assume that the ordinance’s ban on slavery continued after statehood, believed that any restriction Congress placed on Missouri would be similarly perpetual. Southern politicians believed that Missouri, like the states carved from the Northwest Territory, would be free to legalize slavery after statehood. This question was never fully settled, for the final Missouri Compromise, negotiated a year later, allowed Missouri to preserve slavery in its state constitution. Another provision admitted Maine (previously part of Massachusetts) as a free state, while Thomas’s provision banned slavery in the remaining federal territories north of 36°30’ latitude.

Thomas’s provision intentionally left unanswered the question of whether northern territories could legalize slavery after statehood. Thomas and most southern politicians believed they could, while northerners generally believed the opposite. Such ambiguity was intentional and necessary to “gain a majority in Congress” (p. 169). President James Monroe and his cabinet also avoided a definitive interpretation on this point, though few other historians have recognized the importance of this ambiguity to the Missouri Compromise. The proslavery...