Western wheat grass (Agropyron smithii); photo by Matt Lavin on Flickr (use permitted with attribution / share alike).
Official State Grass of South Dakota
South Dakota designated western wheat (Agropyron smithii) as the official state grass in 1970. This variety of wheat is a common native grass in South Dakota - it's used primarily as feed for livestock but also harvested for its seed (wheat grass is also a state symbol of North Dakota). All State Plants & Grasses