Río Cuarto (rēˈō kwärˈtō) [key], city (1991 pop. 138,996), Córdoba prov., central Argentina, in the W Pampa, on the Río Cuarto. It is the commercial center for a large agricultural area yielding fruit, flour, and cattle. The city was settled in the 18th cent. The movement to overthrow Juan Perón in 1955 began at the air force base in Río Cuarto.