Three attempts were made to establish a colony where the city of Buenos Aires stands. The first was in 1535 by Don Pedro de Mendoza with a large and well-equipped expedition from Spain, which, through mismanagement and the hostility of the Indians, resulted in complete failure. An expedition sent up the river by Mendoza founded Asunción, and thither went the colonists from his "Santa Maria de Buenos Ayres" when that settlement was abandoned. The second was in 1542 by a part of the expedition from Spain under Cabeza de Vaca, but with as little success. The third was in 1580 by Don Juan de Garay, governor of Paraguay, who had already established a half-way post at Santa Fé in 1573, and from this attempt dates the foundation of the city. The need of a port near the sea, where supplies from Spain could be received and ships provisioned, was keenly felt by the Spanish colonists at Asunción, and Garay's expedition down the Paraná in 1580 had that special object in view. Garay built a fort and laid out a town in the prescribed Spanish style above Mendoza's abandoned settlement, giving it the name of "Ciudad de la Santissima Trinidad," but retaining Mendoza's descriptive name for the port in appreciation of the agreeable and invigorating atmosphere of that locality.

Buenos Aires remained a dependency of Asunción until 1620, when the Spanish settlements of the La Plata region were divided into three provinces, Paraguay, Tucuman and Buenos Aires, and Garay's "city" became the capital of the latter and also the seat of a new bishopric. The increasing population and trade of the La Plata settlements naturally contributed to the importance and prosperity of Buenos Aires, but Spain seems to have taken very little interest in the town at that time. Peru still dazzled the imagination with her stores of gold and silver, and the king and his councillors and merchants had no thought for the little trading station on the La Plata, for which one small shipment of supplies each year was at first thought sufficient. The proximity of the Portuguese settlements of Brazil and the unprotected state of the coast, however, made smuggling easy, and the colonists soon learned to supply their own needs in that way. The heavy seigniorage tax on gold and silver, and the costs of transportation by way of Panama, also sent a stream of contraband metal from Charcas to Buenos Aires, where it found eager buyers among the Portuguese traders from Brazil, who even founded the town of Colonia on the opposite bank of the estuary to facilitate their hazardous traffic.

In time the magnitude of these operations attracted attention at Madrid and efforts were made to suppress them, but without complete success until more liberal provisions were made to promote trade between Spain and her colonies. In 1776 the Rio de la Plata provinces were erected into a vice-royalty, and Buenos Aires became its capital. Two years later the old commercial restrictions were abolished and a new code was promulgated, so liberal in character compared with the old that it was called the "free trade regulations." Under the old system all intercourse with foreign countries had been prohibited, with the exception of Great Britain and Portugal - the former having a contract (1715 to 1739) to introduce African slaves, and permission to send one shipload of merchandise each year to certain colonial ports, and the latter's Brazilian colonies having permission to import from Buenos Aires each year 2000 fanegas of wheat, 500 quintals of jerked beef and 500 of tallow. The African slaves introduced into Buenos Aires in this way were limited to 800 a year, and were the only slaves of that character ever received except some from Brazil after 1778, when greater commercial activity in the port created a sudden demand for labourers.

Under the new regulations 9 ports in Spain and 24 in the colonies were declared puertos habilitados, or ports of entry, and trade between them was permitted, though under many restrictions. The effect of this change may be seen in the exportation of hides to the mother country, which had been only 150,000 a year before 1778, but rose to 700,000 and 800,000 a year after that date. (For the later history of the city see Argentina.)

(A. J. L.)