In the summer of 1955, two men, both of them white, abducted a 14-year-old African-American boy named Emmett Till from his great-uncle's house in Money, Miss. Roy Bryant and J.W. Milam beat Till almost to death, gouged out one of his eyes, shot him in the head and then dumped his body — weighted by an enormous cotton-gin fan tied with barbed wire — in the Tallahatchie River.
Their motive: Till, visiting from his native Chicago, had reportedly flirted with — or, according to some accounts, spoken "disrespectfully" — to Bryant's wife a few days before.
When an all-white, all-male jury acquitted Bryant and Milam of kidnapping and murder in September, the verdict shocked observers across the country and around the world. And when, mere months later, the men openly admitted to Look magazine that they had, in fact, mutilated and murdered Till, the outcry was so intense — and the reaction of Till's devastated family so dignified — that it lit a spark that helped ignite the modern civil rights movement.
Liz Ronk, who edited this gallery, is the Photo Editor for LIFE.com. Follow her on Twitter @lizabethronk.