McMillin was a resident of
Maysville, Kentucky. His name is often recorded as James McMillan or James McMillen. His widow once testified that McMillin "kept his slaves in the basement of his kitchen."
Bedford Forrest beginning in 1853, and
Bolton, Dickens & Co., Forrest and McMillin had a profit-sharing agreement in which McMillin received 25 percent of revenue above expenses on enslaved people that were purchased for resale at Forrest's negro marts in
Memphis, Tennessee, and
Vicksburg, Mississippi. In 1850, notorious Lexington, Kentucky, trader
Lewis Robards paid McMillin to kidnap a legally free woman named Arian Belle, and her four-year-old child Martha, from
Mason County, Kentucky, in the middle of the night. According to the
Maysville Eagle by way of the
Louisville Daily Courier: At some point before his murder, McMillin sold a young person named John Burnett, who later, under his current name of John Cook, placed a family reunification ad in the newspaper in 1886, hoping to find his lost mother and sister, or perhaps his mother's other sons: ==Death==