How Bruce Jenner became an Olympic icon exactly 39 years ago

— -- Before we were introduced to Caitlyn Jenner, Bruce Jenner captured the hearts of America exactly 39 years ago Thursday by winning the gold medal in the men's decathlon at the 1976 Summer Olympics in Montreal.

Jenner became an instant celebrity and was proclaimed "the world's greatest athlete." Not only was it a significant athletic achievement for the country in its bicentennial year, but the fact Jenner was able to dethrone Soviet decathlete Mykola Avilov, who had won gold in 1972 during the height of the Cold War, made it even more memorable.

Most people under the age of 40 know Jenner best as a reality television star from "Keeping Up with the Kardashians" and most recently "I Am Cait," but the gold medal performance on July 30, 1976, remains the moment Jenner became an indelible part of American history. For some, it's a fading memory about a person whose life since has been rebooted. To celebrate the anniversary, here are five things you might not know -- or remember -- about Jenner's Olympic triumph nearly two decades ago.

How Jenner's iconic flag wave came to be

The signature moment of Jenner's historic accomplishment didn't come during any of the ten track and field events of the competition. It came right after he finished second in the 1,500-meter run, the final event of the decathlon, with the gold medal clinched. As Jenner was still gathering himself, a fan ran onto the field and handed Jenner a small American flag on a stick before being escorted away by security guards.

"What am I going to do with this?" Jenner later said he thought to himself. "I can't put it down, it would look unpatriotic. Creating a spectacle was the last thing I would have done. It just wasn't my style."

So Jenner slowly lifted the flag in the air and waved it emphatically as the crowd roared, creating one of the most indelible images in the history of the Games. Now it's almost hard to image a gold medal moment at the Olympics not ending with an athlete waving or draped in his or her country's flag.

"That moment changed the Games," Jenner would later say. "I had the flag in my hand and it really started something."

Jenner competed in the 1972 Olympics -- and finished 10th

The seeds for Jenner's record-breaking performance in 1976 were planted four years earlier in Munich. Jenner had surprisingly qualified for the 1972 Olympics despite having competed in the decathlon for only two years. He wasn't expected to win, but he set a personal goal of finishing in the top ten and was happy when he finished 10th. But Jenner's outlook on the decathlon and life changed after he watched Avilov win gold for the Soviet Union.

"For the first time, I knew what I wanted out of life and that was it, and this guy has it," Jenner said. "I literally started training that night in midnight, running through the streets of Munich, Germany, training for the Games. I trained that day on through the 1976 Games, 6-8 hours a day, every day, 365 days a year."

By 1975, Jenner was the No. 1 decathlete in the world after setting a record of 8,524 points at a meet in Eugene, Oregon, and improving on that record with 8,538 points at the Olympic trials. His goal in Montreal was not only to win the gold, but break the 8,600-point barrier. The Olympic record set by Avilov four years earlier was 8,466 points.

Jenner trailed after the first day of the decathlon

Despite three personal bests on the first day of the decathlon at the 1976 Games, Jenner went to bed that night 35 points behind the leader, Guido Kratschmer of West Germany. Jenner, however, knew he had won the gold when he left the Olympic Stadium that night.

"The second day has all my good events," Jenner told ABC after the first day. "If everything works out all right, we should be ahead after it's all over."

In the decathlon, points are earned based off the performance in each event, not on the position finished. Jenner was strong as expected in discus, pole vault and javelin on the second day, all but clinching the gold medal heading into the final event, the 1,500-meter run. But he wasn't content with that. After falling well behind event favorite Leonid Litvinenko of the Soviet Union, Jenner made a strong surge to close the gap. He couldn't catch Litvinenko, but his personal-best time of 4:12.61 put an exclamation point on his performance and pushed his point total to a record 8,618.

Jenner knew it would be his final competition

When it was over, Jenner knew he would never compete again. That was the plan all along. In fact, he left his vaulting poles in the stadium. He would never need them again. He had a feeling if he won the gold medal, he would be set for life in the aftermath.

"In 1972, I made the decision that I would go four years and totally dedicate myself to what I was doing, and then I would move on after it was over with," Jenner said. "I went into that competition knowing that would be the last time I would ever do this."

Jenner knew he would get endorsement deals after winning gold, but even he later admitted he never expected to become an overnight celebrity the way he did. He simply figured he wouldn't have to sell insurance again. He would not only become the face of Wheaties, but a spokesperson for Tropicana, Minolta and Buster Brown shoes while also gracing the cover of numerous magazines, from GQ to Sports Illustrated.

"After the Games were over," Jenner said, "I happened to be the right guy, at that right place, at that right time."

Avilov and Jenner were reunited last year

Avilov, the man who inspired Jenner to chase Olympic glory, finished third in 1976, behind Jenner and Kratschmer. Avilov retired four years later and went on to coach in Iraq, Ukraine, China, Egypt and Seychelles.

Jenner and Avilov reunited and took a picture at a track and field convention last year, and Jenner smiled when recalling the meeting during the interview in April with ABC's Diane Sawyer in which he announced, "For all intents and purposes, I am a woman."

"I ran into [Avilov] last year," Jenner said. "I love the guy, but he was terribly overweight and terribly out of shape. And I'm thinking to myself, I've won that battle too!"