When Gilbert Dean was born on 27 April 1840, in Lancaster Township, Fairfield, Ohio, United States, his father, John Dean, was 27 and his mother, Rachael Hite, was 24. He married Ann Maria Edmundson on 8 November 1866, in Indiana, United States. They were the parents of at least 3 sons and 4 daughters. He lived in Bates, Missouri, United States in 1900 and West Boone Township, Bates, Missouri, United States for about 10 years. In 1860, at the age of 20, his occupation is listed as farmer. He died on 1 January 1925, at the age of 84, and was buried in Sharon Cemetery, Coldwater Township, Cass, Missouri, United States.