MEMPHIS, Tenn. -- Elvis Presley was only 21 when he first opened in Las Vegas in 1956. It was at the New Frontier Hotel, where a 30-foot marquee of the entertainer invited guests to hear "The Atomic Powered Singer."The two-week engagement turned out to be a mismatch. "Elvis wasn't ready for Vegas, and Vegas wasn't ready for Elvis," says Graceland archivist Angie Marchese. One of his records, "Heartbreak Hotel," became his first No. 1 hit during the 1956 appearance, but the audience of older Vegas gamblers gave the hip-swiveling newcomer only a "lukewarm welcome."It would take 13 more years before the singer returned to the Vegas stage in 1969. By then he was one of the biggest legends in show business. His sold-out concerts broke all attendance records, and his stage costumes were a big part of the attraction.Those costumes are a major part of a new exhibit, "Elvis: Live from Vegas," in the Sincerely Elvis Museum in Graceland Plaza.