The federal district, created in 1880 to resolve the differences between unitarios (unionists) and federales (federalists), is today the Ciudad Autónoma de Buenos Aires (Autonomous City of Buenos Aires; CBA). It is the oldest and most consolidated section of the AMBA, and is the headquarters of the national government and contains the main public and private institutions. Its area is approximately 200 sq km and the population figures have remained steady since the middle of the 20th century at around 3,000,000 inhabitants. The CBA is surrounded by the districts of Buenos Aires province (PBA) with an approximate area of 3,600 km² and a population of nearly 9,000,000. Its current urban centers were once independent towns that were progressively absorbed into the urban agglomeration as the main city expanded. The metropolis is the urban continuity made up of the two jurisdictions. In the AABA (Environmental Atlas of Buenos Aires) it is known as the Metropolitan Area of Buenos Aires (AMBA); the National Institute of Statistics and Census (INDEC) calls the same area the Greater Buenos Aires Agglomeration. As such, the boundaries of the AMBA are those defined by the INDEC for the last national census in 2001.