 It was only in 1957, that Río Negro acquired status of a province; its first provincial governor was Edgardo Castello of the Radical Civic Union (UCR).Río Negro is one of the six provinces that make up Argentine Patagonia.It is bounded to the north by the Colorado River which separates it from La Pampa Province, to the east by the Atlantic Ocean and to the west by the Andes and the Limay River (serves as the natural border with Neuquén Province).