Areason why slavery developed in the american colonies was

Slavery first began in the Jamestown colony because the colonists were making their money off of planting and growing crops like tobacco and wanted the help from more people(slaves). They mainly used slaves from Africa because their home was far away so it would be hard for them to run away back home. 

There was a need for cheap labor in the colonies. 

African americans at the time just came out of slavery and needed money to provide for there families. so they joined for the money mainly.