Final answer:
The American colonists of the 1600s settled along the seacoast and rivers primarily to carry out trade, which was a part of the mercantilist approach of the British Empire. These locations facilitated the exchange of goods and bolstered economic activities, being central to the export of raw materials and the import of goods not produced in the colonies.
Step-by-step explanation:
A major reason the American colonists of the 1600s chose to settle along the seacoast and rivers were so that they could carry out trade. The colonies were a crucial part of the mercantilist system, allowing the British Empire to amass wealth by controlling the trade of raw materials and manufactured goods. The Navigation Acts, for example, were laws that regulated colonial trade for the benefit of the empire. Settlements along the coast and rivers facilitated easier and more efficient transport of goods to and from the colonies, thus enhancing their commercial activity. These areas were ideal for the exportation of raw materials and for receiving imported goods that were not produced locally.
Also, during the colonial period, the availability of fertile land encouraged settlers to engage in agriculture, which became quite profitable under the mercantilist policies. Settlement locations not only supported trade but also provided the necessary resources for basic sustenance and economic growth, though manufacturing on a scale competitive with England was not the initial focus of the American colonies.