Written By: Ben Cosgrove

In the spring of 1963,  popular from his big-screen breakout as one of The Magnificent Seven and just a couple months from entering the Badass Hall of Fame with the release of The Great Escape, Steve McQueen was on the brink of superstardom.

Intrigued by his dramatic backstory and his off-screen exploits—McQueen was a reformed delinquent who got his thrills racing cars and motorcycles—LIFE sent photographer John Dominis to California to hang out with the 33-year-old actor and, in effect, see what he could get, photo-wise.

Three weeks and more than 40 rolls of film later, Dominis had captured some astonishing images—photos hard to imagine in today’s restricted-access celebrity universe. Here, LIFE.com presents a series of pictures many of which never ran in LIFE, along with insights from Dominis about the time he spent with the man who would soon don the mantle, “the King of Cool.”

Trailing Steve McQueen was Dominis’ first Hollywood gig. “I liked the movies, but I didn’t know who the stars were; I was not a movie buff,” Dominis, who died in 2013, recalled. But he got the assignment because he and McQueen shared one vital passion: car racing.

“When I was living in Hong Kong I had a sports car and I raced it,” Dominis said. “And I knew that Steve McQueen had a racing car. I rented one, anticipating that we might do something with them. He was in a motorcycle race out in the desert, so I went out there in my car and met him, and I asked him, ‘You wanna try my car?'”

Later the two men zipped around Los Angeles together. “We went pretty fast as fast as you can safely go without getting arrested and we’d ride and then stop and trade cars. He liked that, and I knew he liked it. I guess that was the first thing that softened him.”

From early morning until late at night, Dominis followed McQueen through his action-packed days: camping with his buddies, racing his various vehicles, playing with his family, tooling around Hollywood. Even back then, Dominis recalled, he had to be mindful that his constant presence did not become irritating.

“Movie stars, they weren’t used to giving up a lot of time,” he said. “But I sort of relaxed in the beginning and didn’t bother them every time they turned around, and they began to get used to me being there.

In 1963 McQueen had been married to Neile Adams for seven years (they had two young children) but the spark between them was still very much alive. “They were always necking!” said Dominis, who also remarked upon their childlike way with each other in notes he filed for LIFE’s editors back in ’63: “They chase each other around,” he wrote, “as though it were going out of style.”

“With strangers, I can’t breathe,” McQueen told LIFE. “But I dig my old lady.”

“I was very surprised” when Steve and Neile divorced in 1972, Dominis said. “But I lived in New York, and I never saw them [after the shoot was over]. We weren’t real friends, but we were friendly. They had a silver mug made: ‘To John Dominis, for work beyond the call of duty.’ I’ve still got it today.”

At the beginning of the LIFE shoot, McQueen participated in a 500-mile, two-day dirt bike race across the Mojave Desert.

“These people are not the wild motorcycle bums who go roaring through town a la Brando [in The Wild One],” wrote Dominis in his notes. “Rather they comprise doctors, lawyers, businessmen, mechanics, and others who enjoy the competition and the open country.”

Not only was he one of the few competitors to complete the race, LIFE reported, but he also led his amateur class for most of the way, until his bike broke down three miles from the finish.

“He liked camping, he liked rugged things, he liked firing a gun,” said Dominis. (“I’d rather wake up in the middle of nowhere than in any city on earth,” he told LIFE.)

He also very much liked his cigarettes: Like many Hollywood stars of the time, McQueen was an unapologetically heavy smoker, and did not break the habit until he became sick in the late ’70s.

Seventeen years after Dominis made these photos, the actor died at 50 years old, suffering a heart attack following a risky operation to remove the cancerous tumors laying waste to his body. Though Dominis never saw or spoke with McQueen after 1963, he continued to follow his movies, and cherished those three weeks they got to know each other.

“He was very open and playful,” recalled Dominis, “and just doing the things that he loved to do.”

Liz Ronk edited this gallery for LIFE.com. Follow her on Twitter at @LizabethRonk.

At his bungalow in Palm Springs, Steve McQueen practices his aim before heading out for a shooting session in the desert, 1963.

At his bungalow in Palm Springs, Steve McQueen practiced his aim before heading out for a shooting session in the desert, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen driving on Sunset Strip, 1963.

Steve McQueen driving on Sunset Strip, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen and Neile Adams, his first wife, target-practice with their pistols in the California desert, 1963.

Steve McQueen and Neile Adams, his first wife, target-practiced with their pistols in the California desert, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen and Neile Adams, his first wife, in the California desert, 1963.

Steve McQueen and Neile Adams, his first wife, in the California desert, 1963.

John Dominis; Life Pictures/Getty Images

McQueen works out at the gym at Paramount Pictures while making the movie Love With the Proper Stranger opposite Natalie Wood, 1963.

McQueen worked out at the gym at Paramount Pictures while making the movie Love With the Proper Stranger opposite Natalie Wood, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen lifts weights, 1963.

Steve McQueen lifting weights, 1963.

John Dominis; Life Pictures/Getty Images

McQueen takes a call in the living room of his eclectic home in Hollywood, 1963.

McQueen in the living room of his eclectic home in Hollywood, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen and his wife Neile Adams lounge on the patio by the pool at their Palm Springs bungalow, 1963.

Steve McQueen and his wife Neile Adams by the pool at their Palm Springs bungalow, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen, Palm Springs, 1963.

Steve McQueen, Palm Springs, 1963.

John Dominis; Life Pictures/Getty Images

At his Palm Springs bungalow, Steve McQueen puts on a record, with LPs by Miles Davis, Sonny Rollins and Frank Sinatra scattered at his feet, 1963.

At his Palm Springs bungalow, Steve McQueen put on a record, with LPs by Miles Davis, Sonny Rollins and Frank Sinatra scattered at his feet, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen dances with his wife, Neile, 1963.

Steve McQueen with his wife, Neile, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen with his wife, Neile, 1963.

Steve McQueen with his wife, Neile, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen takes a lunch break during a motorcycle race with Bud Ekins, his friend and stuntman for The Great Escape, 1963.

Steve McQueen taking a lunch break during a motorcycle race with Bud Ekins, his friend and stuntman for The Great Escape, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen makes a stop at a grocery store in Pearblossom, Calif., to get some treatment for race-bloodied hands, 1963.

McQueen at a grocery store in Pearblossom, Calif., getting treatment for race-bloodied hands, 1963.

John Dominis; Life Pictures/Getty Images

McQueen takes a deep swig of a tall, cool drink, 1963.

McQueen taking a deep swig of a tall, cool drink, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen on a camping trip, 1963.

Steve McQueen on a camping trip, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen in his sleeping bag on a camping trip, 1963. "This is it, man," he told LIFE. "I'd rather wake up in the middle of nowhere than in any city on earth."

Steve McQueen in his sleeping bag on a camping trip, 1963. “This is it, man,” he told LIFE. “I’d rather wake up in the middle of nowhere than in any city on earth.”

John Dominis; Life Pictures/Getty Images

Steve McQueen, 1963.

Steve McQueen, 1963.

John Dominis; Life Pictures/Getty Images

Steve McQueen, 1963.

Steve McQueen, 1963.

John Dominis; Life Pictures/Getty Images

With his dog, a Malamute named Mike, by his side, Steve McQueen takes in the scenery, California, 1963.

With his dog, a Malamute named Mike, by his side, Steve McQueen in California, 1963.

John Dominis; Life Pictures/Getty Images

More Like This

people

Michelle Obama: Her Inspiring Story

Night with Frank Sinatra people

A Night Out With Sinatra

Christian Dior people

Christian Dior’s Conquering Eye

people

Celebrities’ Best Friends

George H.W. Bush and family at home in 1971. Left-Right: Nephew Billy, daughter Dorothy, George H.W., son Neil, wife Barbara, nephew Jon. people

The Family Life of a Young George H.W. Bush

John Wayne photo essay by John Dominis for LIFE magazine, 1969. people

Behind the Scenes With John Wayne, 1969