In the South, the belief grew that Northerners were using slavery as a smokescreen behind which they could resurrect the Federalist Party and strengthen the central government at the expense of states’ rights. For nearly 30 years, the compromise worked, with two states being admitted together, one slave, one free.

35.5175° N, 86.5804° W

35th parallel

The Missouri Compromise of 1820 established the latitude 36°30′ as the northern limit for slavery to be legal in the territories of the west. As part of this compromise, Maine (formerly a part of Massachusetts) was admitted as a free state.

In 1820, amid growing sectional tensions over the issue of slavery, the U.S. Congress passed a law that admitted Missouri to the Union as a slave state and Maine as a free state, while banning slavery from the remaining Louisiana Purchase lands located north of the 36º 30′ parallel.

Northerners were angry that the ban of slavery under the Missouri Compromise was ended. Both northerners and southerners became more angry with each other, many began to see slavery as a moral issue. The south was happy, but the north was angry because the ruling meant slavery could spread west.

In the South, most slaves did not hear of the proclamation for months. But the purpose of the Civil War had now changed. The North was not only fighting to preserve the Union, it was fighting to end slavery. Throughout this time, northern black men had continued to pressure the army to enlist them.

Their strategy was to take advantage of their compact geography, with internal lines of communication, their military heritage (Southerners had been disproportionately the officers of the United States Army), and their greater enthusiasm for their cause to wear down the Union will to wage war.

For 110 years, the numbers stood as gospel: 618,222 men died in the Civil War, 360,222 from the North and 258,000 from the South — by far the greatest toll of any war in American history.

A soldier was 13 times more likely to die in the Civil War than in the Vietnam War. One reason why the Civil War was so lethal was the introduction of improved weaponry. Massive frontal assaults and massed formations resulted in large numbers of deaths.

American Civil War casualties are those soldiers, both Union and Confederate, who died, were wounded, went missing or were captured. Of those who died, by far the leading cause of death was disease. The exact number of dead will never be known with any certainty.

20 million deaths

(sources and details of figures are provided in the footnotes)

Russia

19,240 fatalities

Battle of the Somme