Two sources found for George, 1861 marriage to Margaret S Bailey, and their 1880 US Census record, both give his name as Carlock. No record for George Carback, spouse Margaret, were found. I also found no children of this marriage. HL Tardy 29 Oct 2018
"Iowa Marriages, 1809-1992," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:XJGC-JYM : 10 February 2018), George M. Carlock and Margaret S. Bailey, 13 Jun 1861; citing Mahaska Co., Iowa, reference 2:3Q55DN1; FHL microfilm 985,381.
"United States Census, 1880," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M6XQ-12C : 7 September 2017), George M Carlock, Jefferson, Harrison, Missouri, United States; citing enumeration district ED 297, sheet 124C, NARA microfilm publication T9 (Washington D.C.: National Archives and Records Administration, n.d.), roll 0689; FHL microfilm 1,254,689.