Mary Smith McClain, better known as Walking Mary and later Diamond Teeth Mary, was born in Huntington, West Virginia, on August 27, 1902. Mary is a half sister of Bessie Smith (Smith's mother was one of Mary's four stepmothers) and witnessed the tragic end of Bessie's life. Mary recalled " Bessie was lying in a hospital waiting room, her arm hangin' by a thread and bleedin' in a pan while the white doctors stood by and watched doing nothin'. They let her die." At the age of 13, Mary couldn't stand the beatings any more and left home to join the circus disguised as a boy in her brother's clothes. She ended up in Memphis, Tennessee, worked as a chorus girl and eventually was picked up by the Rabbit Foot Minstrels, with whom she became a featured singer. Mary spent the twenties and thirties performing in a variety of medicine and minstrel shows. She shared billings with Bessie Smith, Billie Holiday, Sarah Vaughan, Big Mama Thornton, Ray Charles, Charlie Parker and Duke Ellington. She toured with the USO and has sung at the Apollo theater in New York, at the Smithsonian, and at the White House where her show-stopping charisma invariably would get the standing-ovation audiences in the spirit.

Mary had lived with baseball great Satchel Paige, and was never short of stories which astonished and amazed. One evening in Memphis while visiting Bernice Turner, one of Hank Williams' original drifting cowboys, Mary recalled a young Elvis Presley "would bring Howlin' Wolf and me liquor from the liquor cabinet." During the '40s, Mary had diamonds removed from a bracelet and set into her upper and lower front teeth, creating a dazzling stage effect. As BLUES REVUE QUARTERLY magazine founding editor Bob Vorel wrote in 1992, "Although confined to a wheelchair, Mary is still an electrifying performer. Her 'shining smile' and 'chair dancing' brought the cheering crowd down to stage front at both the Handy Awards and King Biscuit Blues Festival."

Diamond Teeth Mary has graced the stage of just about every top blues venue in the country, earning the respect and admiration of fans and musicians alike: Johnny Copeland said "Mary is why I became a musician. I remember peeking under the tent when the medicine show came through town. She was the big star and I was the little boy who said I want to be on that stage too." John Lee Hooker remembered Mary's shows so well that, when sharing the bill at the Las Fontanas, he said "I'm not gonna follow Mother Mary, she'd take the house down!" Big Mama Thornton on Mary, "She's my mother. She took me off the back of a garbage truck in Montgomery, Alabama. I was dressed like a boy and she put ribbons in my hair." Mary adds "I put her into show business. Could she sing!" Buddy Guy once told an interviewer of peeking through a club window as a young boy to get a look at "that lady singer with diamonds set in her teeth." The diamonds, in fact, earned McClain her nickname, and although the original stones were sold to help pay her mother's medical bills, she later gained a new set of teeth, new diamonds, and her first album release, IF I CAN'T SELL IT, I'M GONNA SIT ON IT on the Big Boss label.

Diamond Teeth Mary died on April 4, 2000. At Mary's request, her ashes were sprinkled on the railroad tracks in West Virginia where she hopped her first train. Her gowns are in the Florida State Museum and the Memphis Blues Museum. Miami's famous blues club, Tobacco Road, named the performing room upstairs the Diamond Teeth Mary Cabaret in her honor.