John Sappington Marmaduke was born on March 14, 1833, in Saline County, Missouri, into a prominent political family. His father, Meredith Marmaduke, was the eighth governor of the state and a staunch Unionist before and during the Civil War. But it was the political lead of his uncle, a pro-secessionist governor of Missouri, Claiborne Fox Jackson, which Marmaduke followed in the critical opening months of the Civil War.