Supporters climbed lampposts, jostled for position on roof tops and walls, and fathers held children on their shoulders to catch a glimpse of the City players aboard an open-top bus.
"Days like this are why we came to City, and it's just fantastic," said Sky Blues midfielder Gareth Barry, one of many high-priced players who joined the team in the last few years after it was bought by wealthy Abu Dhabi owners. "Our fans have always been amazing, and they're showing it here today. I've got memories I'll treasure for the rest of my career."
While the celebrations were in full force in Manchester's main square, United's dejected players were arriving at an end-of-season dinner that had an unusually solemn mood - two contrasting images that showed just how much the football landscape has changed in the northwestern city.
"It's been an emotional roller coaster," City fan John Wilkinson said. "I have followed City since the early '90s, so when it went 2-1 I was really down and thought we had blown it. I can't put into words what this means."
And there's no reason to think City's successes will end here.
After enduring relegations and financial chaos while United won 12 of the last 19 English titles, the team derided as "noisy neighbors" by United team manager Alex Ferguson have used their newfound wealth to overtake United, as the country's top club.
"I hope City will become a great club in the world," midfielder Yaya Toure said.