Does anyone know where to find land value trends going back to the 90's broke down by the county level? I've found some numbers state wide on NASS.USDA.GOV but would love this broke down by county. Wondered if anyone knew a database or agency that would know. Thanks!

http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do;jsessionid=F154BA78C7C50C021C8CA924EDB72FD5?documentID=1446