pampas (pămˈpəz, Span. pämˈpäs) [key], wide, flat, grassy plains of temperate S South America, c.300,000 sq mi (777,000 sq km), particularly in Argentina and extending into Uruguay. Although the region gradually rises to the west, it appears mostly level. Precipitation decreases from east to west. Trees are found only along watercourses. Covered by grasses whose height varies with the amount of rainfall received, the soil of the pampas is very fertile and supports a thriving pastoral and farming economy. The Pampa, c.250,000 sq mi (647,500 sq km), of central and N Argentina embraces parts of the provinces of Buenos Aires, Santa Fe, Córdoba, and La Pampa. Cattle was first introduced to the region by the Portuguese in the 1550s. Throughout the colonial period under Spain, only a small part of the Pampa was used; economic activity was practically restricted to primitive stock raising for the exportation of hides, tallow, and jerked beef. Herds of cattle roamed freely over the Pampa, and the gaucho, the Argentine cowboy, was the region's dominant figure in the 18th and early 19th cent. A new economic era was initiated in the second half of the 19th cent., when a growing European market for agricultural products (along with new technology for the shipment of food products) brought immigrant farmers (mostly Italian, Spanish, French and German) to the Pampa. They spread westward with the expansion of the railroad that was built to link the increasing number of ranches with the coast. Settlement spread into the interior, and land was brought under the plow as unfriendly Native Americans were driven out of the region and the gaucho yielded to the farmer. In the 20th cent. agriculture remains the chief economic activity of the Pampa; livestock grazing and wheat growing are found in the drier W Pampa while corn and other grains along with dairying and truck crops are found in the more humid E Pampa. In the seaboard cities of Buenos Aires, La Plata, and Bahía Blanca and in the river ports of Rosarío and Santa Fe are the only considerable industries; meatpacking and food processing are important. The region has a dense transportation network focused on Buenos Aires. The Pampa contains most of Argentina's population.