SAN LUIS  , a province of Argentina, bounded N. by Rioja, E. by Cordoba, S. by the La Pampa territory and W. by Mendoza . Area, 28,535 sq. m . Pop . (1904, estimated) 97,458 . San Luis belongs partly to the semi-arid pampa region, and partly to the mountainous region of the eastern Andes and Cordoba whose ranges terminate between the 33rd and 34th parallels . It is one of the least important of the Argentine provinces because of its aridity and lack of available resources . The rough northern districts, where an occasional stream affords irrigation for a fertile soil, are noted for a remarkably uniform, dry, mild and healthful climate . The Rio Quinto has its sources in these ranges; the Desaguadero, or Salado, forms its western boundary; and the Conlara flows northward among its broken ranges to the great Salinas of western Cordoba . Only in the mountains are these streams available, as they soon become impregnated with saline matter on the plains . The southern part of the province is a great, arid, saline plain, practically uninhabitable . Agri-culture and grazing occupy some attention in the north, but are handicapped by lack of water . The mountains are rich inminerals, however, and a number of gold mines have been opened .

The exports include

cattle, hides, skins, wool and ostrich feathers . The capital is San Luis (pop . 1904, about 10,500) on the Arroyo Chorillos, a little S. of the cerro called Punta de los Venados, 374 M. by rail (the Argentine Great Western) W. of Rosario, and magnificently situated on a plateau 2490 ft. above sea-level . Next in importance is the town of Mercedes or Villa Mercedes (pop . 1904, about 6000) on the Rio Quinto, an important railway junction where the railways from Buenos Aires, Rosario, Mendoza and San Jose unite . San Luis, the capital, was founded in 1697 by Martin de Loyola and was for nearly 200 years only a frontier outpost . It suffered much in the civil wars of 1831-1865 .