Mickelson finished his level in the 73rd round in the 72nd hole. The crowd cheered with joy as the 50-year-old stopped his last shot in the round to confirm his victory.
The San Diego native raised his arms in the air and hugged the box, his brother Tim, after winning his sixth Grand Slam title and confirming his second PGA Championship victory. Won the championship in 2005.
The player, nicknamed Lefty, became the oldest player to win a major tournament. The old brand, owned by Julius Boros for 53 years, was founded in 1968. He won the PGA Championship at the age of 48.
Brooks Kopka and Luis Ostwiesen finished second in the tie, two hits behind Mickelson.
Koepka, who was on top of the board momentarily after the first hole, scored 74, while Oosthuizen played 73.
Shane Lowry, Padraig Harrington, Harry Higgs and Paul Casey shared fourth, four hits behind Mickelson.
Of the Canadians, Corey Konners was 11th, while Adam Haddwin was 64th.
A jubilant crowd for a historic moment
The euphoria was in the eighteenth hole when Mickelson confirmed anything but his expected victory by stopping a 15-foot-long shot with his 9. Thousands of fans had gathered behind him on his trophy march – a scene only seen at the British Open under normal circumstances.
The crowd started chanting his title as he made his way to the tent to hand over his scorecard, his last assignment of the week. A week is not about to be forgotten.
Michelson became the first player in history to win the PGA Tour by 30 years. He won his first of 45 titles in 1991.
Michelson’s victory came a week after he accepted a farewell to compete in the US Open. Ranked 115th in the world and without a win for two years, Michelson couldn’t qualify.
He hadn’t finished in the top 20 in his last 17 tournaments, but against the best golfers – 99 of the world’s 100 best – Mickelson didn’t even look bored this weekend.
Mickelson’s achievement was highlighted by another golf legend, with Tiger Woods praising his win in a Twitter post, qualifying the moment
“Alcohol scholar. Twitter lover. Zombieaholic. Hipster-friendly coffee fanatic.”