valley
Capitalize when it is part of a place-name or follows a river's proper name:
Mississippi River Valley
Mississippi Valley
but valley of the Mississippi
Nile Valley
the valley of the Nile.
Exception: Valley of Mexico.
Capitalize when it is part of a place-name or follows a river's proper name:
Mississippi River Valley
Mississippi Valley
but valley of the Mississippi
Nile Valley
the valley of the Nile.
Exception: Valley of Mexico.