Allen is a city in the province of Río Negro, Argentina. It has 26,083 inhabitants as per the 2001 census. It is located on the left-hand sid…Allen is a city in the province of Río Negro, Argentina. It has 26,083 inhabitants as per the 2001 census. It is located on the left-hand side of the Alto Valle of the Río Negro, near its beginning in the confluence of the Neuquén and Limay rivers, about 20 km west of General Roca and 35 km east of Neuquén.