It appears from the census data that his given name was John "Magruder" High - hence the 'Mack".
If you look at 1870 vs 1880 - almost all the sons appear to be called by their middle rather than first names! Parents Benjamin M High, mother Margaret Caldwell.
U S Census, 1910 Spartanburg Ward 4, Spartanburg, SC
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self Mack C High M 48y South Carolina
wife Estella High F 44y New York
son Elmore High M 19y South Carolina
dau Maude High F 16y North Carolina
dau Minnie High F 13y North Carolina
dau Ruth High F 7y South Carolina
South Carolina, Deaths, 1944-1955
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Estelle Mrs. Benedict High
death date: 20 Apr 1953 Columbia, Richland, SC
Female age 87y est birth 1866
Married spouse Mack C. High
father Joseph A. Benedict
mother Emily Smith
U S Census, 1880 Beech Springs, Spartanburg, SC
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self Bery M. High M 51 SC
wife Margret M. High F 52 SC
son Gavan P. High M 22 SC
son J. Magruder High M 19 SC
son W. Palmer High M 16 SC
son Dubose A. High M 13 SC
daughter Hattie R. High F 9 SC
granddau Marian L. Poole F 0 SC
U S Census, 1870 Beechspring, Spartanburg, SC
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Benj High M 40y SC
Margret High F 42y SC
Perry High M 13y SC
Lee Sarah High F 11y SC
John High M 8y SC
William High M 6y SC
Andrew High M 3y SC
