As early as 1651, the English government had sought to regulate trade in the American colonies, and Parliament passed the Navigation Acts on October 9 to provide the plantation colonies of the south with a profitable export market. The Acts prohibited British producers from growing tobacco and also encouraged shipbuilding, particularly in the New England colonies. Some argue that the economic impact was minimal on the colonists, but the political friction which the acts triggered was more serious, as the merchants most directly affected were also the most politically active.