Maybe it was the moment the Blackhawks marched triumphantly onto Wrigley Field's outfield grass with Lord Stanley's Cup.
Maybe it was when the capacity crowd screamed its lungs out to Jim Cornelison's rendition of the National Anthem.
Maybe it was the moment in the seventh inning, when the already frenzied crowd noticed that they were watching dual no-hitters.
Whenever it was, somewhere along the way Sunday night, Chicago realized it had a front-row seat to all that is good and right in sports on a magical evening won't soon be forgotten.
The night had it all.
It had joy, hatred, disbelief and plenty of I-can't-believe-this-is-happening moments.
It had two rival factions of fans, known for hating each other, standing unified in jubilation and gratitude before the game. Then, as obviously as they'd banded together, they broke back into their separate camps during a game that defied logic and appealed to the heart.
Yes, for one magical night, Chicago was the epicenter of the sporting world.
And it felt damn good, no matter where your rooting allegiances lay.
Sure, the Cubs won the series-finale 1-0. But the night was about so much more than a box score could ever reflect.
It was about three teams, all different, coming together on the pitching mound for the photo-op of the century.
It was about Cubs pitcher Ryan Dempster - a serious hockey fan - raising the Cup above his head. About Sox manager Ozzie Guilen doing the same.
It was about two scuffling teams becoming part of a championship atmosphere and allowing their fan bases to remember what this is all about.
"It never died down," Cubs center fielder Marlon Byrd said of the buzz. "If that's what the playoffs are like, I want to get there."
The teams, who have won one combined title in the past 93 years, played a game that, while just one of 162, seemed to take on a much more important tenor. Ted Lilly and Gavin Floyd matched each other out for out, not unlike two dueling goaltenders stone-walling shots during the Blackhawks playoff run.
Floyd's bid ended 20 outs in and Lilly's three short of completions after a Juan Pierre single.
It was raining by the point, but it was going to take a lot more than a little dampness to ruin this parade on the North side.
"I would have really liked to get this accomplished for my team and this city," Lilly said afterward, a reflection of the contagious culture of civic pride the Hawks inspired.
Lilly said the whole dugout was atwitter from the moment the champions took the field to the end of the game.
The Hawks, too, were acutely aware of just how unique the experience was.
"It's really unbelievable to be a part of," Patrick Kane said. "The fans are unbelievable no matter where you are."
The 21-year-old, whose whirlwind victory lap has taken him seemingly everywhere since his historic goal Wednesday night, joked that he'd catch up on sleep later.
The fruits of victory are just too sweet.
And perhaps that was the most meaningful - and possibly - hopeful thing to come out of Sunday.
If there was any doubt, the nationally-televised lovefest cemented for the country what we here already know. Chicago loves a winner. Reward the city with a title and it will reward you back with an outpouring of adoration. If the alleged two million people who showed up at Friday's tickertape parade didn't drive that home, the 40,456 at Wrigley did.
That fact was not lost on the players from both teams.
"We talked about it when the Blackhawks were walking around the field," Cubs catcher Koyie Hill said. "I came up to [Lilly] and said, 'let's do that.'
"To see how much fun [the Hawks] were having carries over to what we're doing."
For baseball in this town, that can only be a good thing. Even if thing continue going as they have for both teams this year, no one can take away this near-flawless night away.
Very rarely is there a game with four winners.
Then again, Sunday was not your typical night.
Not for the Hawks, Cubs or Sox.
And, most importantly, for the city.