- Species Common Name Tygh Valley Milkvetch
- Species Scientific Name Astragalus tyghensis
- State Listing Status Threatened
The Columbia Plateau ecoregion was shaped by cataclysmic floods and large deposits of wind-borne silt and sand earlier in its geological history. It is dominated by a rolling landscape of arid lowlands dissected by several important rivers, and extends from the eastern slopes of the Cascades Mountains, south and east from the Columbia River to the Blue Mountains.