The Hooper Branch Nature Preserve is located in the extensive dune and swale topography of the sand deposits of northeastern Illinois. The plant communities present at the time of this survey were similar to those of pre-settlement times. The vegetation associated with the dunes had not been disturbed except for past grazing; the swales, in contrast, were drained and farmed before the area was dedicated in 1986. Dry and dry-mesic sand savanna was associated with the dunes where Quercus velutina (Black Oak) accounted for 75% to 97% of the importance value in the savanna. Carex pensylvanica (Pennsylvania Sedge) was the dominant ground cover species usually followed by Schizachyrium scoparium (Little Bluestem). In parts of the preserve that had been most recently burned, woody species were more common in the ground layer, with the most important being Q. velutina seedlings, Rhus copallina (Dwarf Sumac), and Rubus allegheniensis (Common Blackberry). A 3-ha flatwoods in the Preserve was dominated by Q. palustris (Pin Oak), which accounted for nearly 95% of the overstory.