I am in the process of adding alternate names to all of the Grubaugh census listing where the name "Grubaugh" was misspelled or mistranscribed. Hopefully, when these alternatives can be searched, they will be of considerable help to you in your Grubaugh research.
There are many such entries. The Grubaugh name is not easy to spell and there were many census takers guilty of bad handwriting. In order to ensure accuracy, I have charted every person who ever had the Grubaugh surname and lived sometime during the 1800-1930 time period. I have accumulated birth and death dates for most of these people and searched for the census listing of each person who should have been alive during the time of that particular census. I also verified that there were no census listings for people who had reportedly died prior to that census. For example, some researchers list the death date of George K. Grubaugh as 24 Nov 1904. This is an error. He actually died on 30 Apr 1930 and can be found in the 1910, 1920 and 1930 census listings. There were some Grubaughs (particularly females who changed their surname when married) who presented tracking problems. As of now, I haven't entered the Grubaugh maiden name as an alternative name in the ancestry files. If this first step works well, I will include those findings.
There are still some census omissions, but I now believe that most of them reflect less than 100% coverage by the census itself. That is, people who were alive at the time of the census, but were not enumerated. If I couldn't find a person in a particular census, but wasn't sure if that person was indeed alive during the time of census, I categorized the missing entry as "questionable". If a person was still alive at the time a particular census and wasn't found, I categorized that person as "missing".
Here are the results of the searches by census year -
1850 - 90 found, 22 dead, 10 missing (91.8%)
1860 - 138 found, 41 dead, 2 missing, 2 questionable (98.4%)
1870 - 184 found, 48 desd, 14 missing, 5 questionable (93.4%)
1880 - 262 found, 65 dead, 21 missing, 7 questionable (93.1%)
1900 - 448 found, 135 dead, 12 missing, 27 questionable (95.9%)
1910 - 532 found, 188 dead, 28 missing, 31 questionable (94.4%)
1920 - 624 found, 251 dead, 60 missing, 37 questionable (91.9%)
1930 - 783 found, 326 dead, 73 missing, 47 questionable (92.1%)
Here are the alternative Grubaugh entries that I've added so far:
1850 - 11 entries
1860 - 44 entries
1870 - 58 entries
1880 - 90 entries
1900 - 85 entries
I'll be entering 1910, 1920 and 1930 next week.
I would be glad to share with you any results or findings. You can contact me by e-mail at firstname.lastname@example.org