Might want to send for his death record, may get some clues there:
Oregon Death Index, 1903-98
Name: Knight, Augustus County: Douglas Death Date: 11 Dec 1909 Certificate: 4395
Seems there was some confussion on his birth place/date.On the 1880 census he is 30 (1850) bn SC, 1900 he states born aug 1837 SC, on later records his kids sometimes list father born in TEN or Kentucky
1880 WA, Cowlitz Co....as Augusta Night 1900 OR, Klamath Co, 1910 OR, Douglas Co.....his widow is listed with daughter Lillian and Alice and they show father bn in KY.