James F. Jelks was born around 1842 in Mississippi to Frederick A. Jelks and Sophia Cohen. His mother died on April 13, 1844, and his father died in December 1849. He was raised by his stepmother Margaret Jelks, and he grew up in Hinds County, Mississippi. By 1860, he was living in East Feliciana Parish, Louisiana.
He enlisted in the Confederate army in September 1862, and he mustered in as a private in Company E of the 1st Louisiana Cavalry. The regiment took part in the Battle of Stones River, the Battle of Chickamauga, and the Knoxville campaign. He surrendered as part of General Richard Taylor’s army on May 4, 1865, and he received his parole on May 12, 1865.
Jelks settled in Morehouse Parish, Louisiana, after the war, and he earned a living as a farmer. He died sometime after 1870.