The Rio de la Plata (or River Plate) is the estuary formed from the combination of the Uruguay River and the Parana River. It is a funnel-shaped indentation on the southern coast of South America, 180 miles (290 km) long. Where the rivers join it is 30 miles (48 km) wide, increasing to 136 miles (219 km) wide where it opens on the Atlantic Ocean. It forms part of the border between Argentina and Uruguay, with the major ports of Buenos Aires in the southwest and Montevideo in the northeast.
An estimated 2 billion cubic feet (57 million cubic meters) of silt is carried into the estuary each year, where the muddy waters are stirred up by winds and tides. The shipping route from the Atlantic to Buenos Aires is kept open by constant dredging.
The Rio de la Plata is also a habitat for the rare La Plata Dolphin.
See also Battle of the River Plate.