At the time of settlement, portions of the Inner Bluegrass plateau were occupied by a savanna-woodland, in which Fraxinus quadrangulata, Quercus macrocarpa, Q. muhlenbergii, and Q. shumardii were prominent members and now constitute the chief species in the surviving remnants. The interaction of several factors, including past climatic conditions, chemical nature of the bedrock, underdrainage, soil character, fire, and grazing, was undoubtedly responsible for the establishment and maintenance of this vegetation type prior to settlement. The original ground cover was replaced soon after settlement by cool-season pasture grasses. The remnants of the blue ash-oak savanna-woodland are being threatened by the failure of seedlings to become established and by the continued urbanization of the Inner Bluegrass.