The objective of the USDA-NRCS U. S. Rapid Carbon Assessment program (RCAP) is to develop a national soil carbon (C) map using detailed soil spatial and attribute data (SSURGO) with validation against National Cooperative Soil Survey (NSCC) data.  Numerous studies involving soil C have been conducted in the northern Great Plains over the past several decades.  We attempted to develop a data base including past research in order to enhance the RCAP in this region.  We will discuss the process of collecting and evaluating data from past research studies as well as the challenges of interpreting this data to provide useful data to contribute to the RCAP effort.