Final answer:
The middle colonies' most economically valuable natural resource was rich and fertile soil.
Step-by-step explanation:
The middle colonies' most economically valuable natural resource was rich and fertile soil. This allowed for the growth of crops such as wheat, barley, and rye, which were in high demand. The abundance of agricultural resources in the middle colonies made them prosperous and contributed to their economic success.
Learn more about the resources of the middle colonies