Brian Mitchell's second-grade teacher set him straight: No Black man ever had been the lieutenant governor of Louisiana — and he was wrong for saying his ancestor, Oscar Dunn, had been just that.

The class made fun, and "I still feel the sting," Mitchell writes 45 years later in the introduction to his new biography, "Monumental: Oscar Dunn and His Radical Fight in Reconstruction Louisiana" (Historic New Orleans Collection).

It reads like a comic book story of panels and pictures, and the first page shows the scolded 8-year-old Brian at his school desk thinking, "How could she not know?"

He knew for sure, because his great-grandmother said so. His "grandmaw" kept chickens in her backyard in New Orleans and a scrapbook of family memorabilia, and she told him Dunn was a "big deal."

Oscar James Dunn: He could plaster walls, this big guy, and play the guitar, and he was elected lieutenant governor of Louisiana in 1868 — the nation's first Black lieutenant governor.

Grandmaw said never to forget who Dunn was, and young Brian never did. He grew up to become the go-to guy among historians for his knowledge of Dunn and Dunn's achievements — the subject of his doctoral thesis. Mitchell is assistant professor of history at the University of Arkansas at Little Rock.

He wanted even more people to know about Dunn, who was his great-great-grand — call it distant cousin, Mitchell says, the exact genealogy being nowhere near as interesting as the story he uncovered.

"I could have focused strictly on an academic book," he says. Instead, "I took a very different approach — something unique in Reconstruction history," so one-off that he went with a new name for it: "graphic history."