Which of the following allowed the middle colonies to thrive? The location of the middle colonies along the coast made them an important center for trade. Poor agricultural conditions forced colonists to turn to timber, fishing, and other industries that boosted the economy. The lack of diversity among the population fostered harmony and led to fewer disagreements among colonists. Good relations with American Indians throughout the 1600s and 1700s led to peace, unlike in New England or in the South.