I know the county of Grand Forks on their web site has a GIS property search section, where you can find the tract (parcel) of land in the township you want and it will among other things tell you how much land is assessed (i.e. value given it by the county). I dont know of any site which shows recent sales for the GF area for either land or homes.
County of Grand Forks
Click on GIS property search and then zoom in over the township/city of interest. This may or may not be what you were looking for....but is the only thing I know out there avbl on the web. Otherwise you would need to see someone at the county building in downtown GF.
Dan