La Plata River Mouth

The Río de la Plata is a vast estuary formed by the waters of the Paraná and Uruguay rivers. It widens toward the Atlantic, its shallow banks and channels making navigation a demanding task. Indigenous peoples lived along its shores and rivers long before European ships arrived.

In 1516 Juan Díaz de Solís entered the estuary while seeking a route west and called its fresh waters the Mar Dulce. The expedition encountered Indigenous inhabitants, and Solís was killed during a landing on the northern shore. Spanish settlement followed: Pedro de Mendoza founded Buenos Aires on the southern shore in 1536, but the settlement was abandoned. Juan de Garay founded it again in 1580, establishing a lasting port on the extensive inland river system.