Why did the North outlaw slavery in the late 1700's while the South expanded slavery?

The North never had much slavery because they really didn't need them. This was because the depended on manufacturing not agriculture. The south depended on cotton so they got slaves to do their work. The more cotton planted the more slave needed to pick it.

During the Civil War, through Lincoln's Emancipation Proclamation, the North outlawed slavery in the South because it would damage the Southern economy, and that would give the North an advantage.

Lincoln at first didn't outlaw slavery in the North because it was unconstitutional. The Constitution states that property can't be taken away from its owner, and slaves were considered property. Since the Confederate States of America was a whole different country, Lincoln used slavery as a weapon of war.

Since the Confederacy seized US forts and property, Lincoln thought he had the right to take away the Confederacy's slaves. The Southern economy depended on their slaves for the production of cotton and almost everything else.

Although the Emancipation Proclamation had little impact at the start, this would give the North an economic advantage in the Civil War. The Republican Party had decided to make the war against slavery itself in order to stop the Southern slaveholders, and after the war, Lincoln had decided to free slaves in all states.