Readers of Mark Twain will remember Cairo as the town Jim and Huck rafted toward on the Mississippi. At the southernmost tip of Illinois, it oversaw the confluence of the Mississippi and the Ohio River, which would take Jim into the free north. But they missed it during a period of heavy fog and instead found themselves drawn into the deep south. After writing this plot twist, Twain put Huckleberry Finn aside for six years, unsure where to go next.

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Preston Ewing Jr.’s book of black-and-white photos, Let My People Go, chronicles that period with highly charged images of confrontation and solidarity; accompanying the photos are interviews with Cairo residents who were active in the movement. Ewing, a native of Cairo, was working for the NAACP in 1967 as an education director, documenting segregation at midwestern schools, when Hattie Kendrick, president of the Cairo chapter, asked the 21-year-old to take over her position. “I was a little reluctant,” Ewing recalls, “but my father encouraged me. As he’d say, each generation has a responsibility to reduce the level of racism that the next generation inherits.”

The incident touched off three nights of rioting and brought the National Guard to Cairo to restore order. As Ewing launched a series of legal challenges against the city, a weekly black newspaper, the East Saint Louis Monitor, offered him a page a week for news of the conflict. He began to indulge his long-neglected interest in photography. “I found out that photographs are a good way of taking up space,” he laughs. “Which was good, because of some of the things that were going on, the photographs were saying more than a story you could write anyway.”

Ewing tries to look forward, but Cairo’s long and tragic history has a way of pulling one back. The truth about Robert Hunt’s death has never been revealed, but Ewing still hopes for an answer. “As certain whites come to me now, telling me different stories about different things that happened back there that I didn’t know, I feel that one day we may even hear something about that one.”