The south wanted slavery mainly because they wanted to be able to have workers but not have to pay them. This way the South could make more money to either buy more slaves, more land, and be able to pay their taxes. This is mainly why the Civil War started. The North didn't like how the South didn't have to pay workers and the North did. The South also depended on slavery to keep the growth of their farms, and plantations good. With out slavery the South would have been much worse.
The South, needed slavery. The North didn't and were more against slavery than the South. The North worked in mills, factories, they owned and operated. The South grew cotton and tobacco. They needed people who would work in the fields for little or no money at all.
The south even used their slaves for the army. They didn't let their best slaves go to war but they let their more uncontrollable slaves go. When the south realized they needed more men in their army they turned to slaves and had them work in factories so whites in the factories could fight. But soon they needed more men again and this time they had slaves go into the army. Most slaves were even offered freedom if they fought in the war.
Slaves, once the Emancipation Proclamation was signed, stopped working as much as they used too. They slowed down and realized that they would be freed soon. Slaves once the War was coming nearer to the end slaves would run away up to the North and join the Army. Some never fought but if they did they were fierce fighters.