Prairie grasslands of Southwestern Washington were full of fescue grasses, dotted with other natives such as tall Garry oaks, huckleberries, yellow prairie violets, and showy yellow balsam root. In the spring, prairies turned bright blue with blooming camas lilies. Camas lily bulbs were a major food source for native peoples–a kind of prairie equivalent to the wapato root that was harvested from the wetlands section of the site. Camas bulbs are said to taste like potato, and become sweeter as they are cooked slowly.

Black-tailed and white-tailed deer lived in Southwestern Washington prairies, as did many birds. A few of the other prairie animals were isolated in this distinct ecosystem long enough to become unique species. Some are now threatened with extinction, such as the Mazama pocket gopher and the streaked horned lark. Some Western Washington butterflies depend on native fescue grasses, and are also endangered now.