United had denied City the chance to wrap up the title last weekend when they came from two goals down to beat their bitter rivals 3-2 at the Etihad Stadium.
It was a tribute to Ferguson's team-building genius that, just two seasons after the departure of the talismanic Eric Cantona, United were once again at the summit - this time thanks to legendary "Class of '92" graduates Giggs, David Beckham, Paul Scholes and the Neville brothers.
The lose for United means that City team can not be displace from the top of the table, thereby given Pep Guardiola his first Premier League title in his second years as that Manager of Manchester United team. Our Time. Our City.
Jose Mourinho's side had kept the title race just about alive with a dramatic 3-2 derby win in their previous game, but a dismal performance against the league's bottom club means they can not now finish higher than second place.
Jay Rodriguez headed home to secure rock-bottom West Brom a win at Old Trafford that was as remarkable as it had looked unlikely.
After starting the title party with his Mancunian wife and his United-supporting father-in-law, City captain Vincent Kompany joined team-mates to raise a glass to their success.
"I think he has to try to keep that level of stability and, from that stability of course will appear the special match with the special performance, like it happened against City".
If Jose Mourinho-coached Man United can win all of their remaining matches, they can reach maximum 86 points in total.More news: Western airstrikes unlikely to impact Assad's war machine
Their squad is crammed full of wonderfully potent performers such as Juan Mata, Paul Pogba, Romelu Lukaku and Alexis Sanchez, yet the Premier League table, which shows them 16 points behind City, does not lie.
City midfielder Kevin De Bruyne, a candidate for Player of the Year, said: "Unbelievable season for us. I think we deserved that punishment for sure".
An 18-match winning run from late August to late December laid the platform for the runaway title victory, and it was only a matter of when it would be clinched.
Guardiola and his players will have the chance to celebrate properly on Sunday when they host Swansea in their next fixture.
"After beating Manchester City we wanted a winning spirit until the end of the season but today was one of those days".
The pinnacle of Arsene Wenger's Arsenal reign remains the "Invincibles" - only the second team to go through an English top-flight season without losing a single game after Preston's unbeaten feat in 1889. "We deserve to be punished".
"I saw lots of people [over] the moon because we won against City".