A. Marshall Clayton was born around 1841 in Georgia to Isaac and Susanna Clayton. His father was a farmer who owned $1,200 of real estate and $150 of personal property by 1860. They lived in Marion County, Georgia, until the 1850s, when they moved to Barbour County, Alabama. By 1860, he was working as a farmer.
He enlisted in the Confederate army in March 1862, and he mustered in as a private in Company C of the 39th Alabama Infantry. The regiment took part in the Battle of Stones River and the Battle of Chickamauga. He died sometime after 1863.