Until 1880 sheep-rearing was concentrated east of the Salado, north and south of Buenos Aires, beginning with a line that passes through Quilmes, San Vicente, Pilar, and Campana, which marks the limit of the suburban zone. In addition it had spread on the right bank of the lower Salado as far as the foot of the Sierra de Tandil, in an area where the first stations date from 1823, though the population did not make much progress until after 1855. About 1880, after the pacification of the Pampa, the sheep-farms began to expand westward. It was then that the wool of the _pasto fuerte_ appeared on the Buenos Aires market. It came from the Azal district in 1870, from Olavarria in 1880, from Bolivar in 1885, and from Villegas in 1890. The Census of 1889 ascribes 51,000,000 sheep to the province of Buenos Aires; that of 1895 gives much the same figure (52,000,000). Detailed comparison of the two enumerations shows that the expansive movement to the west continued, and was completed during this period. The flocks in the north-west zone of the province (Lincoln, Villegas, Trenque, Lauquen) more than doubled; the flocks of the south-west area (Alsina, Puan, Bahia Blanca, Villarino) continued to grow, and increased by a third. Those on the lands of the central Pampa increased threefold. On the other hand, in the departments north and south of the Sierra de Tandil, where colonization is older, sheep-breeding is stationary. The north-east and south-east areas, between the Parana and the Salado, have diminished: one losing a fifth, and the other a half, of its flocks.