George Allabaugh and his son-in-law John Dial, arrived in Crawford Township, in time to be on the tax rolls in 1827 and are listed one after the other on the 1830 census. George's household held himself and his wife, both between age 60 and 70. John's included himself and his wife, age 20 to 30, and two sons under 5 years old.
The two man are listed next to each other on the 1840 census as well. This time George Allabaugh's home includes a 10 to 15 year old male, George age 60 to 70, and his wife age 70 to 80. John Dial's family is "short" one male compared to 1830. He has only one son age 10 to 15 where you would expect two, based on the 1830 enumeration. I know that both of John's older sons lived to be adults, so it would seem that George Allabaugh and his wife had taken in one of John's sons.
Neither George Allabaugh nor John Dial are on the 1850 Census. Instead we find one household headed by John's second-oldest son Thomas, age 23, and including his sister Eliza, age 18, and his brother Evans, 16. Next door is Maria Dyal, 48, with two children Maria, age 9, and Harrison, 6. Maria has no occupation but holds real estate worth $2000; Thomas is a farmer with no real estate. It looks like Thomas was farming his mother's land–the farm that had been his father's.
Those three censuses confirm, in my mind at least, the "rumor" on familysearch and ancestry.com that John Dial's wife's name was Maria Allabaugh. What the rumor did not include was the identity of Maria's parents, who look to all accounts to be George Allabaugh and his wife. I haven't yet learned the name of George's wife.
... where was George Allabaugh?
European settlers in the United States generally moved from East to West, so the logical place to look for him was somewhere east of Ohio. Also, John Dial's oldest son, George, usually said on his censuses that he had been born in Pennsylvania. (This matters if we are correct in concluding that John Dial's wife was Maria Allabaugh, since they must have met before arriving in Ohio if the families were traveling together.) Looking in Pennsylvania, I found this household in Cross Creek Township, Washington County, in 1820:
1 male 45 and over
1 female 16 to 25
1 female 45 and over
1 person engaged in agriculture
If that isn't George and his wife, then I don't know who is, since I didn't find a match anywhere else. That also agrees with this bit of information from the History of Coshocton County, Ohio, 1740-1881 (Newark, Ohio, A. A. Graham & Co, 1881), page 487:
"Beginning about 1832, quite a number of settlers from Washington county, Pennsylvania, poured into this and the adjoining township in Tuscarawas county."
Backing up and looking farther east, I found this family in Coventry Township, Chester County, Pennsylvania, in 1800 and 1810:
1 male under 10
1 male 26 to 44
1 female under 10
1 female 26 to 44
1 male 26 to 44
1 female 0 to 9
1 female 45 or older
If that is George, then he and his wife had at least two children before Maria. Either they died before 1810 or, more likely in the daughter's case than the son's, had married and moved out of the household.
Coventry Township puts George about 15 miles away from Lower Salford Township, Montgomery County, Pennsylvania, home of the immigrant ancestor Christian Allebach, who died in 1746. A transcription of Christian Allebach's estate papers is online at Christian Allebach's estate papers. They name five sons: Christian, David, Peter, John, and Abraham. Various online sources have lists of the sons of those men, but none are named George.
Still, I think "our" George Allabaugh is a grandson of Christian Allebach. The lists might be incomplete–I didn't find the original sources. Or possibly George Allabaugh went by his baptismal name rather than his given name, or vice versa, and the lists include him under the other name. (German custom was for a child to be given a baptismal name in addition to his or her given name. A family could actually use the same baptismal name for a number of children, resulting in sons named John George, John William, etc.)
Note that there were Albaugh or Ahlbach families in Maryland about this time as well. I don't think George Allabaugh was part of that family. They seemed to have kept the spelling of the name closer to the original German, not including a vowel after the "l", and often preserving the "ch" at the end of the name. And I looked in Maryland for George Allabaugh and didn't find him there.
The following resources, which I did not have access to, might provide more information on George Allabaugh: