yungas (yōngˈgäs) [key], region of lowland valleys in the eastern piedmont of the Andes Mts., 5,000–8,000 ft (1,524–2,438 m) high, extending from the Peru-Bolivia border SE into central Bolivia. They receive excessive rainfall and are warm and humid. Although isolated and very difficult of access, the yungas assumed economic importance in the early 20th cent. as a major source of rubber and quinine. Coca, sugarcane, and coffee are grown there. With improved communications the region's economy has grown, especially in the more accessible valleys close to La Paz, Bolivia, which have been developed as resorts.