The 22 year old put to bed the doubts many had of his capacity to get the job done when the heat was on and never again will such a question be asked of him.
"Obviously I have a lot of commitments, photos and interviews and everything," he said when asked if it had sunk in yet. "But it will probably take a little bit of time to sink in. But just to sit here, knowing that I've just won that trophy and following in the footsteps of one of my best friends, Graeme McDowell, last year at Pebble, you know, it's a great feeling. And I got my first Major Championship out of the way quite early on in my career, especially after what's happened the last couple of months. It feels great. And just looking forward to putting myself in the picture for hopefully many more."
The winning margin was by eight over Australia's Jason Day whose round today might not have been his prettiest but the result was. He struggled finding the fairways from the tee for most of the day but when he needed to get it done he did.
Twelve months ago Day had made the decision not to even qualify for this event as he felt his game was not quite ready but today, just as he had done at Augusta National two months ago, he displayed not only his readiness to compete but his readiness to contend to the end.
Day's magnificent par at the last, after finding the rough and the bunker, bears testament to a young player headed for major championship success in the not too distant future. His runner-up finish moves him to the 9th place in the world rankings having started the year in 38th position.
Despite Day's tenacity McIlroy was in a class of his own all week. He broke so many records in this event that it was hard to keep track of them but essentially here are a few.
McIlroy's total of 268 strokes breaks the 72-hole U.S. Open scoring record of 272 previously held by four players "“ Jack Nicklaus, 1980; Lee Janzen, 1993; Tiger Woods, 2000; Jim Furyk, 2003.
McIlroy's total of 16 under par breaks the 72-hole U.S. Open record for most strokes under par previously at 12-under held by Tiger Woods in 2000.
At 22 years, 1 month, 15 days, McIlroy is the youngest U.S. Open champion since Bob Jones, 1923, at 21 years, 3 months, 28 days. He is also the second-youngest player to win a major championship in past 80 years behind Tiger Woods, who was 21 years, 3 months, 15 days when he won the 1997 Masters.
With the victories by Rory McIlroy and Graeme McDowell, both from Northern Ireland, this is the first time there have been back-to-back international winners from the same country since Alec Ross (1907) and Fred McLeod (1908), both from Scotland.
McIlory never gave anyone else a look in on the final day. He opened with a birdie and added another at the 4th. He missed an opportunity at the 9th but then came the near hole in one at the 10th. The roar from the crowd was deafening as McIlroy walked across the bridge to the green at the par three.
He bogeyed the 12th with a three putt but it mattered little as by now he was so far ahead that no-one could possibly catch him.
The American public have taken McIlroy to their hearts. There is nothing brash about him. Jack Nicklaus said today that he is cocky when he needs to be but humble when he needs to be and that about sums him up.
The reception he received as he walked onto every green was a perhaps a reflection on the fact that they no longer have an American to root for and they had taken sympathy on him for his last round demise at Augusta National. They so dearly wanted him to win and he did not let them down.
Day led the chasers but others also had their chances to finish second. Y.E Yang, Lee Westwood and Fredrik Jacobson all made their runs but it would be Day who would emerge with the runner-up medal courtesy of some great up and down play throughout the round.
In the end it would be four golfers who would tie for third namely Yang, Westwood and the two lone Americans in a sea of foreigners, Kevin Chappell and Robert Garrigus.
There are occasions when you know you have been blessed to witness something special this was one of them. Rory McIlroy came of age on the greens of Congressional Country Club and those there will never forget the manner in which he achieved his breakthrough major championship.