South Branch Moose River (Maine)  The South Branch Moose River is a tributary of the Moose River in Franklin County, Maine. Its source () on Caribou Mountain is about from the Canada–United States border, in Skinner (Maine Township 1, Range 7, WBKP). From there, the river winds generally north for  to its confluence with the main stream of the Moose River in Lowelltown (T1, R8, WBKP).