People in the south used slaves because their economy was focussed on things like cash crops (tobacco, cotton, etc.) These crops required a lot of work so farmers and plantation owners could not do it by themselves. So by using enslave persons they could harvest more crops, sell more, make more money, and in return boost the southern economy.
If you want good sources go to wikipedia and look at the sources used in the wikipedia article. DO NOT USE THE WIKIPEDIA ARTICLE ITSELF AS A SOURCE!
Can you be more specific with the question please
Answer: It's a monitor.
Explanation: I believe the answer's that the united states wanted to dominate other cultures. Also, I can't see the whole question, so I'm trying to help you the best I can.