When Isaac Denton Johnson was born in 1825, in Overton, Tennessee, United States, his father, Benjamin James Johnson, was 24 and his mother, Mahala Denton, was 21. He married Sarah Yandle on 25 December 1845, in Greene, Missouri, United States. They were the parents of at least 6 sons and 1 daughter. He lived in Wright, Missouri, United States in 1850 and Mendon, Monroe, New York, United States in 1855. He died on 21 December 1894, in Webster, Missouri, United States, at the age of 69, and was buried in Marshfield, Webster, Missouri, United States.