Why were rivers such as the Mississippi and Ohio used as state borders when they were being created?

Rivers like the Mississippi and Ohio were used as state borders during the creation of U.S. states primarily due to their natural geographic significance and accessibility. They served as clear, definable boundaries that were easy to recognize and navigate, facilitating governance and settlement. Additionally, rivers provided vital resources for transportation, trade, and agriculture, making them practical choices for delineating territory. This approach helped to create manageable political divisions in a rapidly expanding nation.