This book of range maps for Illinois plants is essentially a supplement to the Vascular Plants of Illinois, published in 1955. The supplement contains records concerning some 50,000 new herbarium specimens, representing 1375 species, collected since 1955. The method used is to show, on a county map of the state, every county in which the plant occurs; the old records (1955) are shown by circular dots while the new records (1955-1960) are shown on the same map as squares. Thus a user can see immediately whether new records have been found since 1955.