Why was slave labor not as important to the north as it was to the south?
there was a lack of african americans living in the north.
there were already enough slaves in the north.
the south had a monopoly over slave trade.
the climate did not lend itself to making slave labor profitable.

African Americans had been enslaved in what became the United States since ... It is important to remember, however, that not all slaves worked on large ... Many free white farmers in the South (and North) also put in very long work-days, but the ... slaves were not just powerless victims of their owners and the slave system.

Explanation:

African Americans had been enslaved in what became the United States since ... It is important to remember, however, that not all slaves worked on large ... Many free white farmers in the South (and North) also put in very long work-days, but the ... slaves were not just powerless victims of their owners and the slave system.