This dataset contains the 1:500,000-scale bedrock geology of Ohio. The bedrock geology dataset was originally derived from the 1:24,000-scale bedrock-geology maps, that were created between 1989 through 1998. The bedrock-geology mapping program was initiated in the mid-1980s to perform detailed, 1:24,000-scale bedrock-geology maps. In 1991, the mapping approach was amended to a reconnaissance mapping methodology, but retaining the 1:24,000 scale. Both detail and reconnaissance bedrock-geologic maps were used as the basic information to compile the 1:500,000-scale, Bedrock Geologic Map of Ohio.