Answer:
The correct answer is natural harbors.
Step-by-step explanation:
Due to the lack of natural resources in the Northeast of the United States, trade became a bit difficult.
In this region it was very difficult to do agricultural work due to the shape of its hills and mountains. But luckily, the Northwest has a natural resource from which it can take great advantage and those are the natural harbors.
Because they have canals, rivers and lakes they were able to establish ports there to facilitate trade with other sectors thanks to its rocky and irregular coast. They were also able to develop the fishing activity and do business with merchant ships that come from other regions.
Its great development in fishing activity also created many jobs for the Northeast population. All this allowed them to grow and develop a great business enterprise as is the Megalopolis that has formed on its coasts nowadays.