Dirtsqueezer points out a useful source but ascribes it, I think, to the wrong agency. Throughout the US the federal Natural Resource Conservation Service, NRCS, (fomerly the Soil Conservation Service) produces Soils Reports by County for all 50 States. Your County Ag department will usually have a copy and NRCS has many small regional offices you can visit. Many of these reports are no longer in print so if you get a copy HANG ON TO IT !
Good luck