Francis Marion Kelley was born around 1841 in Illinois to Francis and Elizabeth Kelley. His father was a farmer who owned $1,000 of real estate in 1850. Kelley grew up and attended school in Vermont, Illinois. His father died on October 25, 1853, and he inherited half of the family’s 100-acre farm. By 1860, he was working as a farm laborer, and he owned $1,500 of real estate.
He enlisted in the Union army on April 24, 1862, and he mustered in as a private in Company F of the 51st Illinois Infantry on July 18. According to his service records, he was 5 feet, 8 inches tall, with dark hair and brown eyes. The regiment took part in the Battle of Stones River, the Battle of Chickamauga, the Atlanta campaign, and the Battle of Nashville. He eventually earned a promotion to corporal, and he mustered out on June 16, 1865. He probably returned to Illinois after the war, and he died around 1875.