"United States Census, 1870," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/M46W-4W3 : accessed 09 Aug 2012), George T Mashburn in household of Benjamin F Mashburn, Missouri, United States; citing p. 5, family 30, NARA microfilm publication M593, FHL microfilm 552278.
"United States Census, 1880," index, FamilySearch (https://familysearch.org/pal:/MM9.1.1/M6XW-774 : accessed 09 Aug 2012), Benj. F. Mashburn in household of John D. Cowen, Green, Hickory, Missouri; citing sheet 503A, family 3, NARA microfilm publication T9-0690.
It may be possible to confirm family relationships with George by comparing test results with other carriers of his ancestors' Y-chromosome or mitochondrial DNA.
However, there are no known yDNA or mtDNA test-takers in his direct paternal or maternal line.
It is likely that these autosomal DNA test-takers will share DNA with George: