The West Branch Moose River is a short tributary of the South Branch Moose River in Franklin County, Maine. Its source (45°25′58″N70°37′46″W) is on Caribou Mountain in Merrill Strip (Maine Township 2, Range 7, WBKP), about 2,000 feet (600 m) from the Canada – United States border, which runs along the height of land between the watersheds of the Kennebec River in Maine and the Chaudière River in Quebec.