This year marks the 50th anniversary of TENNIS Magazine's founding in 1965. To commemorate the occasion, we'll look back each Thursday at one of the 50 moments that have defined the last half-century in our sport.

Sports fans love to talk about records that will “never be broken.” Joe DiMaggio’s 56-game hitting streak, Norm Van Brocklin’s 550 passing yards in one game, Wilt Chamberlain’s 100 points in a game: These marks, all set 50 or more years ago, have indeed stood the test of time.

Theoretically, though, they all remain breakable. Once the tiebreaker was instituted at Wimbledon, most tennis fans thought that the 1969 marathon between Pancho Gonzalez and Charlie Pasarell would stand as the longest in the tournament’s history at 112 games. Then along came John Isner and Nicolas Mahut, who played more games, 138, in their breaker-less fifth set alone in 2010.

But if we’re talking about the record for the most dominant single season in tennis history, it’s hard to see how anyone will ever surpass the one that Steffi Graf put together in 1988. Not only did she become the first player in 18 years to capture the Holy Grail of tennis, the calendar-year Grand Slam, she became the first and so far only player to go the Grail one better and add an Olympic gold medal in the same year. The Golden Slam, as it’s now known, stands alone.

Graf was just 18 when she started on her quest, but her run didn’t come out of nowhere; the German had been building toward it since 1984, when she reached the fourth round at Wimbledon at 15 and announced herself as a force to be reckoned with in the future. From the start, Graf played unprecedentedly fast and forceful tennis; no player before her had ever moved with such predatory haste. Her forehand, which she clubbed from every part of the court, was quickly recognized as an evolutionary leap for the shot. Crosscourt, inside-out, inside-in, down the line: Fraulein Forehand hit them all. Once a junior practice partner of Boris Becker, Graf brought a mid-80s power revolution to the women’s game at the same time that her countryman was doing something similar on the men's side. In the process, Graf dissolved the age-old division between net-rusher and baseliner that had defined the biggest rivalry of the previous era, Martina Navratilova vs. Chris Evert.

Still, going into 1988, Graf had one major title under her belt; she had broken through and beaten world No. 1 Navratilova 8-6 in the third set of the previous year’s French Open final. By August of '87, she had taken Navratilova’s top ranking as well, a position she wouldn’t surrender for four years. But speedy Steffi hadn’t left Martina in the dust just yet. The Czech bounced back to beat her in the finals at Wimbledon and the U.S. Open in ’87. The generational tug of war between the two legends was prolonged and ferocious.

But ’88 felt like the dawning of a new era in tennis. The season began with the debut of Flinders Park in Melbourne, and its slow, bouncy new surface, Rebound Ace. The courts helped Graf in two ways: They gave her time to set up and pound her forehand, and they may have aided Evert in her upset of the fast-court-loving Navratilova in the semifinals. Either way, Graf romped to the title without losing a set, and beat Evert in the final. Steffi even frightened a few of her opponents along the way. Janine Thompson, Graf’s second victim Down Under, spoke for many of her fellow players when she said, “We had played only one game when I asked myself, ‘What the hell am I going to do?’”

There was nothing anyone could do four months later at the French Open. Graf again stormed through the draw without losing a set; the only player to even remotely challenge her was Gabriela Sabatini, who managed to take one set of their semifinal to a tiebreaker. In the final, Graf faced a player who had upset Navratilova earlier in the event. This time, though, it wasn’t Evert who helped smooth her path to victory, it was 17-year-old Natasha Zvereva. Smooth was the operative word: Graf’s 6-0, 6-0 win in just 32 minutes would serve as the exclamation point on her season. Graf lost 13 points in recording the first double bagel in French Open final history, and the first in any Grand Slam final since 1911. All Steffi could do when it was over was apologize to the Parisian crowd. “I’m very sorry it was so fast,” she said as she held the trophy.

At Wimbledon, Graf finally got her shot at Navratilova in a major final. Martina was the six-time defending champion, and she was 8-0 in finals on Centre Court. Surely, at 31, she would have to surrender her crown to the 19-year-old No. 1. But using her trustiest weapon against the German, her lefty slice serve into Graf’s weaker one-handed backhand, Navratilova snuck out the first set and went up a break early in the second set. “My backhand was terrible,” Graf admitted later. Was history not going to turn on this day, after all? Was the older generation not going to give way to the new?

The shift came at last with Navratilova serving at 2-0. Two of her deliveries drifted away from Graf's backhand, and the German made her pay with two forehand return winners. Navratilova was broken, and so was the dam: She wouldn’t hold again as Graf won nine games in a row and the first of her seven Wimbledon titles, 5-7, 6-2, 6-1. “It was like trying to stop a runaway train,” Peter Alfano wrote in The New York Times.

“I was confident before the match,” Graf said, “but the first set made me very angry. I just wanted to hang in there, to show I could play much better than I was.”

Even the loser had to admit that the guard in women’s tennis had changed.

“This is how it should happen,” Navratilova said when it was over. “I lost to a better player on the final day. This is the end of a chapter, passing the torch if you want to call it that.”

After grabbing that torch, it was fitting that Graf would complete the last two legs of her Golden Slam against a player of her own generation, Gabriela Sabatini. The Argentine turned 18 that year, and she and Graf often played doubles together.

All of which made for a very tense afternoon when the two friends faced off in the U.S. Open final, with Graf one win from the Grand Slam. To that point, she had been as imperious as ever, losing just 13 games in her first five matches (the sixth was a walkover against Evert in the semifinals). But with history staring her in the face, even Fraulein Forehand took a moment to blink. She lost just her second set at the Slams that year before righting the ship and finishing with an appropriately one-sided 6-1 third-set win. Don Budge, the only American to win the calendar-year Grand Slam, handed her the trophy.

Graf would have a chance to go one better than Budge, and the rest of the sport’s single-year Slammers. In 1988, tennis became an Olympic sport again for the first time since 1924. It was, if nothing else, a chance for Steffi Graf to win another title. After a short post-U.S. Open break, she headed for Seoul, where she lost just one set in running through the draw. Sabatini was waiting for her in the gold-medal match, but she didn’t have to wait long. Graf, with no mid-match hiccups this time, beat her 6-3, 6-3.

The Golden Slam, tennis’s Holy Grail plus one, was a reality. No man or woman has approached it since, and short of the game adding a fifth major, no one will ever break it.