MEMPHIS, Tennessee - Elvis Presley, the United States icon and king of rock 'n' roll, transformed popular culture, sold over a billion records and is idolized as ever on the 40th anniversary of his tragic death.

His Graceland mansion in Memphis, Tennessee - the second most famous home in the United States after the White House - expects more than 50,000 people to descend for the biggest ever annual celebration of his life 40 years after his death aged 42 on August 16, 1977.

Presley is considered the best-selling artist of all time, shifting an estimated billion records. In 2016, Forbes ranked him fourth highest earning dead celebrity at $27 million, still moving a million albums.

"He is the only person of modern times who is instantly recognizable throughout the world by his first name," said British author and artist Ted Harrison, who has written two books about Presley.

"Say 'Elvis' in Beijing, Nicaragua, Estonia or Fiji and you get an immediate recognition across language and culture," he said.

His unique voice and style blended R&B, blues, country, gospel and black music, challenging social and racial barriers at the time, and earning him the nickname "Elvis the Pelvis" for his gyrating moves.

Oozing style, charisma and naked sex appeal, he was the fantasy of millions of women and inspired everyone who came after him, from The Beatles to The Rolling Stones to today's chart-topper Bruno Mars.

"Hearing him for the first time was like busting out of jail," Bob Dylan has said.

In the late 1960s, the composer and conductor Leonard Bernstein called him "the greatest cultural force in the 20th century".

Hits such as Heartbreak Hotel, Hound Dog, Jailhouse Rock and Are You Lonesome Tonight are instantly recognizable. His music has been reissued and repackaged countless times since his death.

More than 20 million people have visited Graceland, his home for 20 years, after Priscilla, his ex-wife and mother of his only child Lisa Marie, opened it to the public in 1982.

The estate says it pulls in 600,000 visitors a year and contributes around $150 million a year to the Memphis economy. Neither is it showing any sign of slowing down.

In downtown Memphis, home of the blues, you can buy everything Elvis - from Christmas tree decorations to luggage. Cardboard Elvis cutouts greet you outside bars and his music blares out of loudspeakers.

"He's the celebrity of all celebrities," said Lisa Bseiso, 36, who set up The Official Elvis Presley Fan Club of Qatar, the Middle Eastern kingdom where she was born and raised.

"Forty years after his death, that's why he's a phenomenon. He's still as powerful, as loving."

Agence France-presse