When Harlan Thomas Killough was born on 22 May 1903, in Mount Clare, Nuckolls, Nebraska, United States, his father, Thomas Donley Killough, was 27 and his mother, Emma Magdelena Zimmerman, was 24. He married Bertha Margaret Dalton in July 1923, in Red Cloud, Webster, Nebraska, United States. They were the parents of at least 2 sons and 1 daughter. He lived in Webster, Nebraska, United States in 1935 and Red Cloud Election Precinct, Webster, Nebraska, United States in 1940. He died in November 1971, at the age of 68.