Why did southerners want to expand slavery westward?

Southerners wanted to expand slavery westward primarily to maintain and increase their economic power, as the plantation system relied heavily on slave labor for crops like cotton and tobacco. They believed that expanding into new territories would secure more land for cultivation, thereby boosting their profits and preserving their way of life. Additionally, there was a desire to ensure that new states would maintain a balance of power in Congress between slave and free states, protecting their political interests.