A colleague with the US Department of Agriculture just sent me this link:
Soil surveys are produced by the National Cooperative Soil Survey, a joint effort
of the United States Department of Agriculture and other Federal agencies, State
agencies including the North Carolina Agricultural Research Service, and local
agencies. The Natural Resources Conservation Service (formerly the Soil Conservation Service) has leadership for the Federal part of the National Cooperative Soil Survey.
Also see the soil survey maps on the North Carolina Maps website.