In sealing the league at this stage, City matched the record for the earliest title win - held by United since 2001.
City are 16 points clear of second-placed United, who can only take a maximum of 15 points from their remaining five games.
As for City, it has a month to finish a season with the most points, goals and wins in a single Premier League campaign.
It is City's fifth English top-flight title, their last Premier League triumph having come in the 2013-14 season.
Broncos Release Running Back CJ Anderson
With Denver likely unable to find another deal, they finally made a decision to cut him. Anderson suggested he'd use the offseason of uncertainty to motivate him in 2018.
Mourinho was less than thrilled with midfielder Paul Pogba's performance, removing him before the hour for Anthony Martial under the guise of making sure the France global did not pick up a second yellow card.
"I am always a great believer that the truth always comes out and it has", he told BBC WM.
"We were masters in complication, everything was complicated".
A 73rd-minute header from Jay Rodriguez after United had failed to defend a corner won the game for relegation-threatened West Brom and Mourinho said his team had not played the simple football he expects.
They won it in the last remaining seconds in 2012, and in the final match in 2014.
Naldo goal seals Schalke win over rivals Dortmund
Konoplyanka's effort proved a sighter as he hammered Schalke in front in the 50th minute. And Naldo drove in from 25 yards after a short free-kick to secure the win.
City manager Pep Guardiola might have missed one of the proudest moments of his career, however, after admitting on Saturday that he had a round of golf booked with his son and was not planning to watch United's game.
Henry, who implored him to emulate his City performance on a more consistent basis, said that such displays prove he can not. "With my experience you don't win titles with inconsistency. Probably because I won eight championships, I was not in the moon with the victory against them because that doesn't make me feel super happy".
A disappointed Juan Mata says Manchester United must shift their focus to a crucial week in their season following their 1-0 loss to West Brom on Sunday. "In my opinion, it affected for sure some of the people that were too happy just with that", United manager explained. "We did not deserve to lose, we gave them opportunity to win the match", he added.
"Everybody will try to improve - like we did from last season".
"My team-mates will roll their eyes as I want to see the reaction from us next season as I've never been able to retain a title".
United Kingdom hit a specific and limited set of targets in Syria: May
DUP leader Arlene Foster said the airstrikes were "limited but proportionate and justified". May said she would address parliament on Monday about the strikes.