city, capital of Río Negro provincia, south-central Argentina. It lies along the western bank of the Negro River 20 miles (32 km) from the river's mouth at the Atlantic Ocean, opposite Carmen de Patagones in Buenos Aires province. A fort called Mercedes de Patagones, built there in 1779 by the explorer Francisco de Viedma, was the capital of the Patagonian territory until the Río Negro national territory was set up in 1884. In 1955, with the creation of Río Negro province, Viedma became the provincial capital. The agricultural potential of the city's environs, long stymied by occasional inundation from the Negro River, was enhanced after 1970 with the assistance of international funds. Viedma received its present name in 1878. Pop. (1999 est.) 56,583.