More than twenty-five percent of the men in Boston had invested in shipping or worked in it. Ship captains and businessmen held most of the public offices.

The American colonies traded goods such as whale oil, ginger, iron, wood, and rum, an alcoholic drink made from sugarcane. Ships carried these goods from the New England colonies to Africa. There, they were traded for black Africans who became slaves in the American colonies.

The Africans had been captured by enemy tribesmen and sold to African slave traders. The New England boat captains would buy as many as they could put on their ships. Conditions on these ships were cruel. The Africans were crowded together and forced to travel in areas so small they could hardly move. Some were kept in chains. Many killed themselves rather than live under such conditions.

Others died of health disorders they caught on the ship. Yet many did survive the trip, and became slaves in the southern colonies, or in the Caribbean islands. Black slaves were needed to work on Caribbean sugar plantations. The southern American colonies needed them to work on the tobacco and rice plantations.

By seventeen fifty, almost twenty-five percent of the total number of people in the American colonies were black slaves. From the fifteen hundreds to the eighteen hundreds, Europeans sent about twelve million black slaves from Africa to America. Almost two million people died on those slave ships.