What movements or events indicated that the Northern and Southern parts of the United States were becoming separate societies in the years 1787 to just before the Battle of Fort Sumter in April, 1861 and why?

Explanation: Slavery arrived in North America along side the Spanish and English colonists of the 17th and 18th centuries, with an estimated 645,000 Africans imported during the more than 250 years the institution was legal.  But slavery never existed without controversy. The British colony of Georgia actually banned slavery from 1735 to 1750, although it remained legal in the other 12 colonies. After the American Revolution, northern states one by one passed emancipation laws, and the sectional divide began to open as the South became increasingly committed to slavery. Once called a “necessary evil” by Thomas Jefferson, proponents of slavery increasingly switched their rhetoric to one that described slavery as a benevolent Christian institution that benefited all parties involved: slaves, slave owners, and non-slave holding whites. The number of slaves compared to number of free blacks varied greatly from state to state in the southern states. In 1860, for example, both Virginia and Mississippi had in excess of 400,000 slaves, but the Virginia population also included more than 58,000 free blacks, as opposed to only 773 in Mississippi. In 1860, South Carolina was the only state to have a majority slave population, yet in all southern states slavery served as the foundation for their socioeconomic and political order.

1820 | The Missouri Compromise

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This 1856 map shows the line (outlined in red) established by the Missouri Compromise. (Library of Congress)

In the growth years following the 1803 Louisiana Purchase, Congress was compelled to establish a policy to guide the expansion of slavery into the new western territory.  Missouri’s application for statehood as a slave state sparked a bitter national debate.  In addition to the deeper moral issue posed by the growth of slavery, the addition of pro-slavery Missouri legislators would give the pro-slavery faction a Congressional majority.  

Ultimately, Congress reached a series of agreements that became known as the Missouri Compromise.  Missouri was admitted as a slave state and Maine was admitted as a free state, preserving the Congressional balance.  A line was also drawn through the unincorporated western territories along the 36°30' parallel, dividing north and south as free and slave.  

Thomas Jefferson, upon hearing of this deal, “considered it at once as the knell of the Union.  It is hushed indeed for the moment.  But this is a reprieve only, not a final sentence. A geographical line, coinciding with a marked principle, moral and political, once conceived and held up to the angry passions of men, will never be obliterated; and every new irritation will mark it deeper and deeper.”

1831 | Nat Turner’s Rebellion

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Nat Turner interpreted two solar eclipses as instructions from God to begin his rebellion. (Library of Congress)

In August of 1831, a slave named Nat Turner incited an uprising that spread through several plantations in southern Virginia.  Turner and approximately seventy cohorts killed around sixty white people.  The deployment of militia infantry and artillery suppressed the rebellion after two days of terror.  

Fifty-five slaves, including Turner, were tried and executed for their role in the insurrection.  Nearly two hundred more were lynched by frenzied mobs.  Although small-scale slave uprisings were fairly common in the American South, Nat Turner’s rebellion was the bloodiest.

Virginia lawmakers reacted to the crisis by rolling back what few civil rights slaves and free black people possessed at the time.  Education was prohibited and the right to assemble was severely limited.  

1846 - 1850 | The Wilmot Proviso

The Wilmot Proviso was a piece of legislation proposed by David Wilmot (D-FS-R PA) at the close of the Mexican-American War.  If passed, the Proviso would have outlawed slavery in territory acquired by the United States as a result of the war, which included most of the Southwest and extended all the way to California.  

35 is your answer because i looked it up