The northern states were more industrious. Factories, smelters, abattoirs, etc. They usually require skilled labor that you couldn't or wouldn't get from slaves. Plus the country was already divided on the issue of slavery from the very beginning. There was even talk of abolishing it outright after the revolution but a compromise was made to preserve the nation. It would be addressed at a later time. Many if not most people in the north didn't see a need for slavery as they had plenty of people to do the labor whereas the south was the opposite and focused more on agriculture.
Record the scene and post it