The largest crowd ever to watch a soccer match was at the 1950 World Cup in Rio de Janeiro when 173,850 paying spectators came to the Maracana for the Brazil-Uruguay final clash, though unofficial estimates put the attendance as high as 210,000.
United's win means they advance to Monday's final in Miami, where they will meet traditional English rivals Liverpool.
The crowd got an added bonus when Cristiano Ronaldo made a surprise appearance for Madrid in place of Alvaro Arbeloa in the 74th minute, having been ruled out of contention before the match with what was reported to be an injured left knee.
Young had opened the scoring in the 21st minute when he capped off a 20-pass move to beat keeperIker Casillas at his near post from about 12 meters.
However, it took United only 10 minutes to regain the lead when Young curled in what looked like a cross from the left. United's England forward Wayne Rooney timed his run perfectly but did not appear to make contact with his attempted header.
His presence distracted Casillas, though, with the keeper reacting too late to stop the ball curling inside the far post.
“I think we were fantastic from the first minute to the end,” Young told Fox Sports.