The Savanna has changed little from the period when eastern settlers first arrived south of the Kankakee River. The soil is a fine sand quartz, which covers the preserve and the areas surrounding it. It primarily occurs in the sand hills, much of the surrounding flatlands contains sand. Savannas in this region are dominated by Oak trees. Oaks survive in the sands which shed water rapidly, creating drought like conditions. Throughout northwest Indiana, the Oak savannas are primarily black oak and white oaks.[2] Typical dry prairie plants include hairy puccoon, Goat's rue, Blunt-leaved Milkweed, leadplant, and New Jersey tea. These are in addition to the grasses listed above.