356 people inhabit this rural unincorporated township, making up a community of knowledgable agriculturalists. Known in the farming community for the Rio Oso Gem Peach (Delicious BTW) and the Oro City Post Office that was established in 1853 and discontinued the same year. Later reestablished from 1855 to 1858. There used to be a town called Oro City near the present site of Rio Oso that was located on the Bear River, three miles above the confluence with the Feather River. The Rio Oso Post Office was established in 1920. The name of Rio Oso means "Bear River" in Spanish.