The Columbia River, Klamath River in northern California, Pit River in northern California, and Fraser River in southern British Columbia are the only four rivers connecting the watersheds on the east side of the Cascade Range to the Pacific Ocean. Each river has created a gorge through the Cascades. The Columbia River Gorge marks the state line between Oregon and Washington, and its wide range of elevation and precipitation makes it an extremely diverse and dynamic place. Ranging from to sea level, and transitioning from of precipitation to only in , the gorge creates a diverse collection of ecosystems, from the temperate rain forest on the western end—with an average annual precipitation of —to the eastern grasslands with average annual precipitation between , to a transitional dry woodland between Hood River and The Dalles. Isolated micro-habitats have allowed for many species of endemic plants and animals to prosper, including at least 13 endemic wildflowers.