The North abandoned slavery when it was economically unviable, not for any moral reason.
Lincoln In his first inaugural address: "I have no purpose, directly or indirectly, to interfere with the institution of slavery in the states where it exists. I believe I have no lawful right to do so, and I have no inclination to do so."
In a letter to Horace Greeley (8-22-1862) Lincoln wrote: "My paramount object in this struggle is to save the Union, and is not either to save or destroy slavery."
The real drive in the North to abolish slavery was to protect the White working man, and to prevent blacks from eventually becoming part of their society.
Not what they taught you in school, is it?