Final answer:
Great Britain and France wanted control over the Ohio River Valley due to its strategic and economic importance as a gateway to western territories and valuable resources.
Step-by-step explanation:
The major reason that both Great Britain and France wanted control over the Ohio River Valley was due to its strategic and economic importance.
The Ohio Valley was a crucial region for both countries in terms of expanding their colonial territories and gaining access to valuable natural resources. Control over the Ohio River Valley would provide a gateway to the western territories and serve as a crucial transportation route for trade and military operations.
Additionally, the Ohio River Valley was a disputed borderland between the French and British colonies, and both powers sought to establish dominance in the region to secure their respective claims and prevent their rival from gaining an advantage.