Location, geography, the availability of coal, lower water tables (a big deal in mining), climate, availability of harbours... the reasons behind the north industrializing before the south are far more complex than slavery.

Imho I think the use of coal for heat allowed colder climates to get going faster than those area where heat wasn't as needed. Shorter growing seasons may also have meant more available manpower. Scotland before England. New York before Mississippi. Europe before Africa.