Bill Johnson after winning the men’s downhill ski race at the 1984 Winter Olympics. (Steve Powell)

Bill Johnson, a onetime car thief who found salvation as America’s rogue of the slopes, winning the Olympic downhill race in 1984 to become the first male skier from the United States to capture a gold medal in Alpine skiing, died Jan. 21 at an assisted-living facility in Gresham, Ore. He was 55.

His death was announced by the U.S. ski team. He had been in declining health since a near-fatal skiing accident in 2001. He had been partially paralyzed since a major stroke in 2010.

Mr. Johnson’s brief, spectacular career was concentrated in a single year, 1984, when he boldly predicted that he would win the gold medal in the downhill at the Winter Olympics in Sarajevo.

Skiers from the traditional Alpine powers in Europe and even some of his teammates considered the 23-year-old Mr. Johnson a brash upstart, as he reveled in his image as the bad boy of skiing. He was called Billy the Kid.

“Basically, any downhill skier is a daredevil, and I’m no exception,” he said before the Winter Games in the former Yugoslavia. “I like to drive cars faster than 100. I like to go over bumps in my car and get airborne. I like to drink. I chase girls full time, but I only drink part time.”

Bill Johnson after receiving his gold medal at the 1984 Winter Olympics. (Michel Lipchitz/AP)

In January 1984, one month before the Olympics, Mr. Johnson backed up his bravado by winning a World Cup downhill race in Switzerland. By the time he got to Sarajevo, his confidence and ability were at their peak.

“I don’t even know why everyone else is here,” he said. “Everyone else can fight for second.”

He was fearless in a sport with one simple goal: be the fastest person down the mountain. The steep, relatively straight Olympic course was ideal for Mr. Johnson. Small for a downhill racer, at 5-foot-9 and 170 pounds, he curled himself into a tight tuck position centered low over his skis.

“I’m built like a bullet,” he said.

In his winning run, Mr. Johnson maintained smooth form as he covered the course at an average speed of 63 mph. The cover of Sports Illustrated showed him flying through the air, with the headline “Flat Out for Glory.”

With a gold medal around his neck and “The Star-Spangled Banner” ringing in his ears, Mr. Johnson was on the top step of the Olympic podium, as skiers from Switzerland and Austria stood below him. He won two more World Cup downhill races in 1984 and talked about the “millions” that would come his way.

“Face it, Bill Johnson is a free spirit,” his Olympic coach, Bill Marolt, said at the time. “The one thing Johnson has that all great athletes have is an unbelievable spirit — the feeling that he can’t be defeated.”

But Mr. Johnson never won another race. Hampered by knee and back injuries, he retired in 1989. He occasionally competed in events for older skiers, but when he was away from the slopes he seemed lost.

He failed to find success as a stock trader, professional golfer, ski-camp operator, real estate broker and electrician. In 1991, his 13-month-old son drowned in the family’s hot tub in South Lake Tahoe, Calif. Several years later, he and his wife were divorced, and she moved out with their twin sons.

Broke, out of work and 40 years old, Mr. Johnson embarked on a quixotic mission to recapture his old Olympic magic. Wearing outmoded skis and uniforms, he did poorly in races, discovering that the sport had changed as he grew older.

On March 22, 2001, while training near Whitefish, Mont., Mr. Johnson lost control at more than 50 mph, slammed face-first into the icy surface and hurtled through two protective barriers.

He was unconscious when rescuers reached him. An emergency tracheotomy was performed at the scene, and Mr. Johnson was taken by helicopter to a hospital, where he spent three weeks in a coma.

His former wife, Gina Ricci, came to his bedside.

“He told me he was going to go back to the mountain,” she told the New York Times, “and he was going to win me back.”

When a friend went to retrieve Mr. Johnson’s pickup truck — a 1984 Ford F-250 — he found a black bag nestled under the seat. It held his Olympic gold medal.

William Dean Johnson was born March 30, 1960, in Los Angeles. His father worked in com­puters.

The family moved to Idaho when Mr. Johnson was 7, then two years later settled in Brightwood, Ore., near Mount Hood. He was a good student and promising skier, but he was also restless and quarrelsome.

Arrested at 17 for car theft, Mr. Johnson was told by a judge that he could go to jail or attend a ski academy in Washington state. He chose skiing, but he never outgrew his reputation as a brawler who fought with his teammates and argued with his coaches. He was once kicked off the national ski team for poor training habits, but for a few brief months when it counted the most, he reigned as the dominant downhill skier in the world.

After his horrific crash in 2001, Mr. Johnson recovered enough to ski for recreation, but he had memory loss and other problems. A series of strokes left him progressively debilitated.

He spent his final years with his mother, D.B. Johnson, who survives him, along with his twin sons. His story was featured in a 2011 documentary, “Downhill.”

Since Mr. Johnson’s gold medal in 1984, the only other U.S. skiers to win the Olympic downhill have been Tommy Moe in 1994 and Lindsey Vonn in 2010.

“Those who know me may say I was a difficult person but fun to be around,” Mr . Johnson said in 1990. “Those who don’t probably will just say I was the best downhill skier in U.S. history. No matter what they say, there’s one thing they’ll never take away from me — I was Olympic champion.”