He had married well, to Lavinia, a daughter of Dr. John Sappington, a pioneering physician in Saline County, Missouri, and his wife Jane, sister of a Kentucky governor.

Marmaduke changed his opinions and developed Unionist leanings by mid-century, but four of his sons served the Confederacy during the American Civil War, and two died.

His son John Sappington Marmaduke was promoted during the American Civil War to become a senior officer of the Confederate States Army.

Her father became a prominent pioneer physician of Saline County, who was later known for his development of a patent medicine, a quinine pill used to treat malaria and other fevers.

[5][1][4] For a brief time, Marmaduke became a partner in his father-in-law's family enterprises, which included stores in Jonesborough (now Napton) and Arrow Rock, Missouri.

[citation needed] While serving as surveyor for Saline County, Marmaduke platted the village of Arrow Rock in 1829.

[3] Saline County is within the region known as "Little Dixie", which was settled by numerous migrants from the Upper South, who developed plantations and held slaves in higher numbers than in most areas of the state.

[citation needed] Marmaduke was a Jacksonian Democrat and a friend and supporter of Missouri Senator Thomas Hart Benton, whom he met through his father-in-law Sappington.

In one of his final messages to the state legislature, he strongly urged the establishment of what was then known as a "lunatic asylum," to house and treat those with mental illness.

Angered by his refusal, Democratic leaders bypassed Marmaduke as their candidate in the 1844 gubernatorial election and chose John C. Edwards, who won the office.

[1] Son Henry Hungerford Marmaduke served as a gunner in the Confederate Navy aboard the ironclad CSS Virginia in its historic clash with the USS Monitor.

Since 1967, the cemetery has been preserved as a State Historic Site as part of a program to recognize burial places of governors.

Recognizing contributions of the many enslaved African Americans he held, Dr. Sappington had established separate land for their use as a burial ground.