1877 birth matches 1900 census. He was listed as 5 on 1880 census.
1880 census district 2, Cannon Co., TN;
GANNON, George, self, m, m, w, 43, TN, farmer, NC, NC
GANNON, Catherine, wife, m, f, w, 40, TN, keeping house, TN, TN
GANNON, Lonzo, son, s, w, 15, TN, TN, TN
GANNON, Nicey A., dau, s, w, 12, TN, TN, TN
GANNON, John G., son, s, w, 10, TN, TN, TN
GANNON, Edward, son, s, m, w, 8, TN, TN, TN
GANNON, Walter, son, s, m, w, 5, TN, TN, TN
GANNON, Timothy H., son, s, m, w, 2, TN, TN, TN
1900 census Cannon Co., TN;
GANNON, George W., self, May 1837, 63, TN
GANNON, Martha, wife, Sep 1860, 41, TN
GANNON, Walter, son, Apr 1878, 22, TN
GANNON, India, dau, Jan 1893, 7, TN
GANNON, Jim, son, Jun 1894, TN
GANNON, Callie, dau, Jun 1895, 4, TN