One of the loveliest native violets is Viola pedata,bird's foot violet, which is most often found in sand prairies and sand savannas. The flowers are relatively large for such a small plant the flowers are about 1.5 inches in diameter while the plants are about 6 inches tall.
Photo taken by K. R. Robertson of plants at Braidwood Dunes and Savanna Nature Preserve in Will County, Illinois.