The land that was to become the State of Illinois was once two-thirds covered by prairie. Big Bluestem (Adropogon gerardii) may have been the most widespread and abundant grass on the prairie. Big Bluestem grows in such tall and dense stands that it often outcompetes other grasses. It grows from three to ten feet tall, depending on soil conditions and moisture. The grass is green throughout much of the summer, but the stem turns a bluish-purple hue as it begins to mature. The seed heads usually have three spike-like lobes and resemble a bird’s foot. Settlers called Big Bluestem “Turkey Foot.” On August 31, 1989, Governor James R. Thompson signed into law a bill designating the Big Bluestem as Illinois’ official prairie grass.