Why did slavery die out in the north by the early 1820's?

One of the major reasons why slavery died out in the North by the early 1820's was because the North was a highly mercantilist-based economy, in which there was very little need for slave labor--unlike in the South, where slave labor was in high demand due to the South's almost entirely agricultural economy. 

Louis xvi wanted to force aristocrats to pay taxes for the first time