When famed magician David Copperfield purchased a rare recording of a Martin Luther King Jr. speech that turned up in someone’s attic a couple of months ago, Laura Crosby got to thinking about some old boxes in her own home.

For four decades, the Summerville woman held onto several boxes of manuscripts, photographs and recordings she inherited after the death of her father — a former newspaper reporter and author. She hadn’t paid them much mind until she read about Copperfield’s tapes, which were initially valued at $100,000.

Crosby and her husband, Birdie, dug into the boxes and carefully examined about six hours worth of 45-year-old tapes recorded by her father, Eugene B. Sloan, while he was employed with The (Columbia) State newspaper.

They listened as a gospel choir sang hymns on one of the tapes, then stopped in their tracks when King’s iconic speaking voice resonated from their speakers.

“You could tell it was him, clear as day. I mean, the tape was so clear you could even hear the people’s footsteps as they walked by,” Crosby said.

The civil rights leader delivered the 40-minute speech in question during a trip to Charleston on July 30, 1967, as part of the movement’s Poor People’s Campaign. This was a tour to draw attention to the plight of the underprivileged.

The Charleston stop took place about a week after racially tinged riots in Detroit, and some locals worried King’s visit might stir up trouble here as well. King denounced that belief in his emotional speech, insisting he would never support riots that hurt the black community more than they helped. No violence followed his visit.

Sloan recorded the speech on a reel-to-reel tape machine. He later wrote an article for The State about the event, under the headline “King Calls For Negroes To ‘Build, Baby, Build.’ ”

Also found on Sloan’s tapes was a meeting of disgruntled Ku Klux Klan members recorded the same weekend as King’s Charleston visit, and a 1969 speech delivered by King’s associate and fellow civil rights leader Ralph Abernathy.

Crosby donated photographs her father took of King to the South Caroliniana Library at the University of South Carolina, where Sloan attended law school.

She said the library was interested in the recordings as well, but for now Crosby has them tucked away in a lock box at the bank.

Acting on the advice of a lawyer, she and her husband made only one copy of the King recording, and she said she doesn’t plan to play it again.

Crosby hopes to sell the recording to someone willing to preserve it.

“My father had a nose for news, but his real love was for preserving history,” Crosby said.

State Sen. Robert Ford was a young member of the Southern Christian Leadership Conference in 1967, and he clearly remembers attending King’s July speech.

Ford said King was always well-received in Charleston, thanks to many of the city’s activists, such as Septima P. Clark and Esau Jenkins.

But Ford questioned the monetary value of Crosby’s recording. Tapes from certain periods in King’s life are more rare, particularly the span immediately following the bus boycott in Montgomery, Ala., he said.

“They’re not going to make the kind of money that they think they’re going to make because it’s nothing new,” Ford said. “I think they might be misguided, because we’ve got too many speeches that are already published from ’67.”

Ford said he had similar recordings from that year, but lost them and much of the rest of his collection of civil rights memorabilia in a house fire in 2008.

Steve Klein, spokesman for The Martin Luther King Jr. Center for Nonviolent Social Change in Atlanta, said King recordings surface sporadically. The center has received about three such recordings this year, but he said he couldn’t speak to their value on the open market.

“There’s been a few lately. We may receive one or two a year, and then a year may go by when nothing pops up,” Klein said.

Reach Christina Elmore at 937-5908 or at Twitter.com/celmorePC.