John K. Clayton was born around 1839 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.
He enlisted in the Confederate army in May 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, the Battle of Chickamauga, the Atlanta campaign, and the Nashville campaign.
He returned to Barbour County, Alabama, after the war, and he married a woman named Jane. They had at least two children: William, born around 1867; and Victoria, born around 1869. He worked as a farmer, and by 1870, he owned $780 of real estate and $450 of personal property. He died sometime after 1870.