What unresolved conflict was made worse by adding more territory to the US in the early to mid-1800s?

The addition of new territory to the U.S. in the early to mid-1800s exacerbated the conflict over slavery, particularly with the Missouri Compromise of 1820 and the Compromise of 1850. As new states were added, the contentious debate over whether they would be free or slave states intensified, increasing regional tensions between the North and South. This unresolved conflict ultimately contributed to the outbreak of the Civil War in 1861.