Review the map above. Why is the red line between Missouri and the Arkansas Territory significant?

The line started the debate that eventually led to the Civil War.
The line gave Congress much needed control over the politics of the rapidly growing Midwest.
The line was important in completing the Mason-Dixon line between the North and South.
The line established a boundary to keep the slave states and the free states balanced in Congress.

The red line between Missouri and the Arkansas Territory was significant because it established a boundary to keep the slave states and the free states balanced in Congress.

Explanation:

The Missouri Compromise was concluded in 1820 in the United States due to disagreements between the free northern states and slave southern states of the United States about the integration of the new states from the Louisiana Purchase. The problem between the two parties was primarily the balance of power in the Senate.

The compromise contained the following main points:

- Missouri would join the United States as a slave state.

-Maine would become a free state, independent of Massachusetts.

-In the future, all states to be founded north of 36° 30' north latitude (the southern border of the state of Missouri) would become free states.

In practice, this compromise has yielded little. Major disagreements arose among states such as Kansas and Nebraska. The large state of California, which is mostly below 36° 30' north latitude, also wanted to join as a free state. This was resolved in the compromise that followed the Missouri compromise: the Compromise of 1850.