The São Francisco River is the fourth longest river system in South America, and, at approximately 1,800 miles, the longest river that lies completely within Brazil.

     The stamp issued by Brazil in 2005 shows a simplified image of the river system. There are four red areas on the main stream. Three of them mark the locations of three large dams, Tres Marías, Sobradinho and Paulo Alfonso. Tres Marías, near the southern end of the river, was completed in 1961, Sobradinho or Itaparica Reservoir, just west of the northern-most point of the river, was filled in 1988, Paulo Alfonso is located at the Paulo Alfonso falls (over 250 feet high) at the north end of the river ,(the large red area east of the north-most point. The dams provide hydroelectric power, urban and industrial water, and water for agriculture. The red area east of that is unidentified.

     On the stamp there are pictures of a hydroelectric plant, people fishing, a waterfall, and a couple of boats in the ocean. I believe the waterfall is the Paulo Alfonso waterfall. The letters on the map indicate seven Brazilian states: PE-Pernambuco, AL-Alagoas, SE-Sargipe, BA-Bahia, GO-Goiás, DF-Distrito Federal, MG-Minas Gerais.