Plants of the Chicago Region & USDA Plants list this species of indigo as native to Lake county & southern counties located along the Ohio river.  
Extremely blue flowers clustered on a loosely branched  shrub. 
Indigo's are in the legume family. They restore nitrogen into the soil. 
Blooms in full to partial sun May-June.
Grows 3-4 ft tall & 4 ft wide in dry to medium soil. 
This plant has a tap root that can reach 7ft in length. 
Does not respond well to being moved once established.
Tolerant to deer, drought, erosion, clay, dry, & shallow-rocky soils.
Attracts butterflies & bees.