Sunnyside is situated adjacent to the Blackwood River 12.5km out of Bridgetown along Tweed Rd. The Carbannup Brook flows from the south and meets the Blackwood River within the reserve, which initially was used as a stock watering point. It was vested with the Shire of Bridgetown -Greenbushes in 1971 for recreational purposes.
Sunnyside Hall was built in 1921 and was first used for monthly dances. The hall and oval are still used for many local activities including the annual Sunnyside New Year's Day cricket game.
Sunnyside has healthy vegetation and a variety of plants, which provide valuable habitat for wildlife. An initial survey has identified 120 species, which include various native buttercups, Running Postman and Native Wisteria, as well as Red and Green Kangaroo Paws. The vegetation is predominantly Jarrah-Marri open woodland with an understory of wattle, pea scrub and native grasses. A number of plants were used by Aboriginal people as food, including the small sweet fleshy fruit of Australian Bluebells, Bardi grubs, which live in the trunks of dying trees and fruits of the Zamia, which requires a lengthy period of treatment to be made edible.