Francis A. Lyon was born around 1844 in Adams County, Illinois. By the early 1860s, he was living in Missouri and working as a farmer. He enlisted in the Missouri militia in 1862 and mustered in as a private in Company E of the 2nd Missouri Militia Cavalry. He eventually earned a promotion to corporal. Two years later, on March 1, 1864, he became a sergeant in Company G of the 13th Missouri Cavalry. According to his service records, he was 5 feet, 7 inches tall, with light hair and gray eyes. He mustered out at Fort Leavenworth on January 11, 1866. He died sometime after 1866.