When Oscar Jackson was born on 25 October 1881, in Pleasanton, Atascosa, Texas, United States, his father, John Santee Jackson, was 31 and his mother, Dosia Milholland, was 18. He married Amanda Ross on 1 January 1903, in Atascosa, Texas, United States. They were the parents of at least 3 sons and 6 daughters. He lived in Justice Precinct 1, Atascosa, Texas, United States in 1910 and Justice Precinct 8, Atascosa, Texas, United States in 1940. He died on 1 November 1948, in Atascosa, Texas, United States, at the age of 67, and was buried in Pleasanton, Atascosa, Texas, United States.