Gurney, the GNIS is a big help but not the final deciding factor. For instance, the GNIS lists districts, streams, mountains, etc. We are concerned wtih counties, cities, towns, populated places, villages, etc. I often check by state fo see if there are multiple places with the same name. We have been using populated places in location categories. Often you will see that they overlap CDPs. We can use them if the place is not ONLY a CDP.