In 1956, when Elvis Presley was just 21 and barely known, a young photographer named Alfred Wertheimer accepted a commission from record company RCA Victor to tag along after the up-and-coming singer from the American south. But what he saw led him to keep tagging along for a whole year, a year that would be one of the most significant of the singer's career.

It was a year that began with solitary train rides and a smattering of fans at the state door, and ended with screaming girls and police security to keep the mobs at bay.

It was the year that Elvis became the phenomenon that so many of the world's musicians would revere, but these photos show something of the person that came before, and give us a sense of who he was.

Wertheimer's photos from 1956 capture a beautiful young man on the cusp of greatness - but already with a definite style and the same work ethic that would later drive him to drugs. The series is now a travelling exhibition developed by the Smithsonian's National Portrait Gallery in Washington DC, and travelling for the first time out of America.

This week, Elvis enters the building at the National Portrait Gallery in Canberra, for a show that's both moving and surprising, even for long-time Elvis fans. Most of us remember only the superstar heart-throb, or the spangled, overweight parody of later years. But Wertheimer, with access remarkable today for its proximity, was able to capture him in various states of contemplation or exhaustion, performing and relaxing, recording or listening to music. In one, he reclines on a sofa with a pile of fan mail that seems, in retrospect, hilariously small. In another, he sits at a counter in a diner, alone, but for a woman standing at an adjacent counter. The woman is black; in the 1950s, segregation was still a fact of life. Paradoxically, many were shocked, once they'd heard his voice, to discover that Elvis was white.

Gallery registrar and resident Elvis fan Maria Ramsden says even the most diehard Elvis enthusiasts will be moved by some of the images in the show.

"It is a really intimate show - it's not just Elvis as you know him, Elvis the performer. That's why I think people who maybe think they're not interested in Elvis, they should come along," Ramsden says. "Wertheimer's actually said that the really interesting thing about Elvis as a subject to photograph was most people will let you get between six or seven feet away from them. Elvis would let you get within a foot, and he didn't seem to be almost aware of the camera … It was absolutely fantastic for a photographer to be able to document a subject who was completely unaware, or wrapped up in whatever he was doing, so you really do get not a posed shot but a really candid shot and a good look into the soul as well."

It is, she says, a fascinating study in stardom - a year in the life of someone who goes from being notable to being extraordinary.

"He was a fairly popular artist before then in the south, in '56, but that's when he really hit real stardom, and it's quite interesting in the way that Wertheimer documented this - you can really see at the beginning, Elvis can be in a public place with maybe just a scattering of fans trying to talk to him. Towards the end of that year he'd be mobbed if he walked out of the house."

And there are hints too, in the show, of the sweet, albeit devastatingly attractive, young man, who came from poverty and wanted to do right by his parents.

"He adored his mum and was devastated when she died. He was a nice boy - he made money and bought his parents a nice house, got them a swimming pool which nobody else did in the neighbourhood," she says.

"He really did look after his family, and I do think he just had that dream of big house, lovely wife, wanted to sing - why would you have any idea at 21 that you would become this legend?"

Wertheimer's photographs were also important when it came to how Elvis's image would become something to be marketed, and that's where his manager, the formidable Colonel Tom Parker, came into his own.

"He was a real Svengali right from the start - he was, I guess, a promoter in that Sideshow Bob kind of way, but also quite forward-thinking with his marketing," says Ramsden.

"He was the first one that actually marketed products related to a star. Not long after Elvis really hit the big time, Colonel Parker had Elvis-branded lipstick out for teenaged girls to buy. Every aspect of his image was controlled so, really, this is the only little window where the Colonel wasn't controlling Elvis's image.

''It's such a pivotal point in his career, I don't think it had clicked with the Colonel. But actually I think probably this process did make him cotton on, when he saw some of these candid shots, it occurred to him, God, I need to control the image of this artist because that's where the money's coming from. And so throughout the rest of his career, the Colonel controlled everything, which is quite sad."

It was because of the Colonel that Elvis never toured outside America, and instead became known to the world primarily through his movies - 33 in all. But Ramsden says Elvis's musical talent became almost a secondary thing to his physical image, and later trainwreck years.

"When you listen to his early songs, they're amazing, they're wild, they're almost proto-punk, they're really something different," she says.

"He was obviously influenced by a lot of musical styles, he listened to a lot of R&B music, he listened to a lot of gospel music, and in fact his gospel songs are absolutely beautiful. He had a stunning voice."

She says it's not surprising that when the Beatles first toured America, their most fervent wish was to meet Elvis.

''I think what [Lennon] meant was Elvis exploded with this musical style that nobody had ever heard before, with the moves and the look … You want to emulate someone like that, someone a little bit dangerous, kind of sweet, who had really the whole kit and caboodle going. But still a very natural boy at that point.''

But there's something almost unbearably poignant, too, in the steadfast gaze of the young Elvis sitting by himself on a train, or shaking his hands dry in a washroom, or even recording a song with a back-up band.

It's moving because we know what comes after. But Elvis, at 21, had no idea.

Elvis at 21 opens at the National Portrait Gallery on December 7 and runs until March 10.