Buenos Aires (rebuilt 1580)

Timeline

1. 1580South bank of the Río de la Plata, near the mouth of the Riachuelo · Río de la PlataJuan de Garay traveled downriver from Asunción and refounded the city on the south bank of the Río de la Plata on June 11, 1580, naming it the City of the Holy Trinity, with the port called Santa María del Buen Aire. This filled the vacuum left after Mendoza's 1536 outpost was abandoned in 1541 due to supply problems and indigenous attacks, placing the estuary once again under Spanish control from the Viceroyalty of Peru.
2. 1580–1583Grid streets of the City of the Holy Trinity · Río de la PlataFollowing Spanish American practice, Garay laid out the plaza, appointed municipal officials, and distributed urban house lots and suburban ranches to the accompanying colonists. Livestock that had scattered in Mendoza's time had bred on its own in the Pampas, allowing the refounded city to rely quickly on ranching rather than being merely a military post. Garay himself was killed in 1583 while traveling north, but the municipal framework was already in place.
3. 1583–1600Port of Buenos Aires · Río de la PlataIn the late 16th century the city's population was still small, yet it had become the transshipment point between the Paraná–Paraguay river system and the Atlantic, through which hides, livestock products, and smuggled goods passed. Official trade remained restricted toward Peru, but its estuary position gradually let it overshadow upstream Asunción as the seaward gateway to the Río de la Plata region.