There's more than one place called '''River Valley''':
Saint John River Valley - in New Brunswick
Breede River Valley - in the Cape Winelands of Western Cape
River Valley - in Arkansas
River Valley (Maine) - in area encompassing Oxford County and part of Franklin County, Maine.
See also:
Connecticut River Valley - in Connecticut
Hudson Valley (Hudson River Valley) - in New York (state)
Miramichi River Valley - in New Brunswick
Red River Valley (North Dakota) - in North Dakota