Review the map above. why is the red line between missouri and the arkansas territory significant?

The line was important because it was established that any new western state that would be south of the line could be a slave state, while any new state in the west north of the line would be a slave free zone. This was done according to the Missouri compromise when slavery was an issue once more in 1850. The line also became the northern border of Texas when it was later added to the union.