732 of the Law on Territorial Development and the Metropolitan Area of San Salvador and neighbouring municipalities.

Since 1990, it was felt that urban development in the Municipality of San Salvador and neighbouring municipalities was having a remarkable growth, and even be defined as a big city.

This situation required the planning and control of urban development in these municipalities and their conformation as a metropolitan area.

Currently, the AMSS constitutes the directional centre of the country in political, financial, economic and cultural life.

The most recently published official population projections for El Salvador forecasted the combined population of the fourteen municipalities at 1,767,102 in 2015, which would constitute 27.4% of the country's projected 6,460,271 inhabitants.