Two hundred years ago, Northern and Southern politicians came together to sign the Missouri Compromise. The bill, which admitted Missouri to the union as a slave state, Maine as a “free” state, and drew a line to the Pacific at 36 degrees 30 minutes (the Southern boundary of Missouri) that was intended to divide slavery from “freedom” forever after, is generally and properly considered a milestone on the pathway toward the Civil War and the conflict over slavery.

But popular memory has forgotten that it did even more than that. For many in Missouri, the statehood question was not simply a debate over slavery, but a purposeful effort to keep all black people, whether enslaved or free, out of Missouri and the West. In fact, the statehood debate was shaped around a de facto compromise between the slaveholding and working-class, anti-black elements of the state’s settler polity.

Understanding the Missouri Compromise in this way points the way to a reinterpretation of the Civil War as something other than a simple conflict between North and South or even slavery and freedom. Rather, the Civil War was a conflict between two interconnected but also antagonistic versions of white American expansion: one premised upon slavery, the other upon freedom not just from slavery but from black people entirely.

While we commonly think of slavery, sharecropping and segregation in the South as driving anti-blackness in American history, the process of western expansion, with the attendant notion of “the white man’s country,” that undergirded the development of cities such as St. Louis and the United States, is equally essential to explaining the power and persistence of anti-blackness today.

On February 13, 1819, Rep. James Tallmadge of New York added a rider to the Missouri Statehood bill that came to consume Congress for almost a year and would ultimately shape the legal history of slavery and constitutional history of the state for the next 45 years. Missouri, Tallmadge suggested, should be admitted to the union only if it outlawed slavery. “This momentous question, like a firebell in the night, awakened and filled me with terror,” Thomas Jefferson wrote.

In 1820 the threat to the union was allayed, or at least delayed, with the Missouri Compromise, one of the most notorious compromises in the history of the United States: Slavery would be allowed in Missouri. In exchange for Missouri’s admission as a slave state, Maine was admitted as a free state. A line was drawn at 36 degrees 30 minutes (the southern border of Missouri) all the way to the Pacific. Below the line, slavery would be allowed; above it, only freedom, or at least the sort of freedom imagined by white settlers and supremacists.

Once a line had been drawn westward to the Pacific and forward into perpetuity, Missouri was given permission to draft a state constitution. Held in St. Louis, the constitutional convention produced a document that threatened to unravel the delicately balanced congressional compromise that had been almost a year in the making. In addition to sanctioning slavery, the Missouri Constitution of 1820 directed the legislature of the new state “to prevent free negroes and mulattoes from coming to and settling in this State, under any pretext whatsoever.”

The provision reflected the particular sort of white supremacy that was characteristic of much of the growing population of the state of Missouri and the city of St. Louis. It was consonant with the politics of the American Colonization Society, which had emerged on the East Coast in 1817, and which sought the ethnic cleansing of the North through the removal of free black people to Africa. In Missouri, however, negro exclusion was given particular resonance with the Indian removal that was ongoing in the state. “The cry has been raised — ‘Missouri for white men!’ ” recalled the free black barber and chronicler of black life in St. Louis, Cyprian Clamorgan. In Missouri, Indian removal and negro exclusion were aspects of the same imperial and territorial project: what the abolitionist William Lloyd Garrison would later call “whitemanism.”

St. Louis was a city populated and inhabited by men on the make — that was why they moved west in the first place; made men stayed at home in the East. Despite its status as the largest city in a state whose admission to the union would soon become so identified with proslavery politics, no other Southern city had such a small proportion of slaveholders among its white population.

Many of these white men were migrants from Virginia, where representation in the state legislature had, like representation in the U.S. Congress, been apportioned on the basis of population rather than suffrage — the three-fifths compromise, most notorious of them all, which provided an enduring political subsidy to slaveholders, who were able to increase their political representation in proportion (3/5) to the number of human beings they owned.

In Missouri things would be different and only “free white male inhabitants” would be counted: The state, under its 1820 Constitution, would be ruled by and for white men rather than slaveholders. For nonslaveholding and working-class white men who predominated in the state, Indians were a barrier to cheap land, slaveholders a threat to their political power and free people of color a threat to their economic independence.

In order for Missouri to be admitted to the union, the state constitution had to be sent back to Washington and approved by the United States Congress. At stake was the question of negro exclusion. Article IV, Section 2 of the United States Constitution provides that “The Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States.” Termed the principle of “interstate comity,” in practice this clause means (and was in 1820 taken to mean) that individual states are not allowed to discriminate against the citizens of other states. The Missouri Constitution of 1820’s deliberate exclusion of the free black citizens of other states declared that when it came to free people of color, the state of Missouri was a territory apart.

A long and unusually pointed debate — the second Missouri Compromise debate, now mostly forgotten — followed. And in February 1821 the final admission to the union of Missouri (and of the state’s apparently unconstitutional state constitution) was approved by U.S. Congress.

Under the constitution of 1820, free black people in Missouri were denizens, not citizens. Much like Indians, they fell under the law of the state without the ability to invoke its provided protections. Under an 1835 law, free black children were legally required to be apprenticed to white families. An 1843 revision to the state code restricted the immigration of all free blacks unless they could demonstrate they were citizens of another state — a near impossibility for most, because states did not issue proof-of-citizenship documents. And in 1847, the state of Missouri explicitly violated the terms of Article IV, Section 2 by reviving the language of the constitution of 1820 and making it state law: “No free negro or mulatto shall under any pretext, emigrate to this state from any other state or territory.” After 1847 it was the legal duty of every justice of the peace, county clerk and judge in Missouri to violate the United States Constitution in the name of whites-only state law.

Rethinking the history of the coming of the Civil War from the West, from the standpoint of imperial expansion, demands we reconsider the racist legacy of the victory of the United States of America over the Confederate States. It helps explain just how deeply ingrained anti-blackness is in American life then, and now.