County records show all of the properties along this way with an address of County Road 17. The county does not refer to Denby Road at all. Not even where I found it on SDDOT's records (https://experience.arcgis.com/experience/c0d19beb93784872bd6dc8a06382010b/#data_s=id%3AdataSource_2-18b24912f29-layer-18%3A1132435).

I have added Denby Road (https://www.openstreetmap.org/way/1347408941) based on SDDOT records.

This area is a bit confusing. It seems like there are very few (if any) signs for anything other than main roads. Unfortunately this is pretty normal in rural areas. It is probably more verifiable by armchair than on foot. I'm going to look this over and try fixing anything obvious. At least it will be a little closer to correct.