When Jacob Milton Allen was born on 3 September 1855, in Bladensburg, Wapello, Iowa, United States, his father, Joseph Crispen Allen Sr, was 24 and his mother, Elizabeth Jane Ingram, was 21. He married Nellie Adell Dimmitt on 4 December 1881, in Story, Iowa, United States. They were the parents of at least 2 sons and 6 daughters. He lived in Mehurin Township, Lac qui Parle, Minnesota, United States in 1910 and Riceville Township, Becker, Minnesota, United States in 1920. He died on 22 June 1950, in Burns, Harney, Oregon, United States, at the age of 94, and was buried in Burns, Harney, Oregon, United States.