What historical reasons did the northerners abolish slavery?

Hello! So America had always been home to people who felt that slavery was wrong and should be eliminated. These people, called abolitionists because they wanted to abolish or destroy slavery, denounced the practice as horrible and evil. Prior to the mid-nineteenth century, however, their efforts to eliminate slavery from U.S. soil failed to gather enough popular support because everyone knew how much the South depended on slaves to make its economy and society work. But in the 1830s and 1840s, organized opposition to slavery in the United States became more powerful and confrontational (meeting an issue head-on) than it had ever been before. Describing slavery as an evil and un-Christian system and a stain on the values enshrined in America's Declaration of Independence, the abolitionists finally convinced large numbers of Northerners that slavery should not continue. So i hope that help!

with my knoladg i would say it was c