The Scotsman arrived at United from Aberdeen in 1986 and was tasked with ending the club's 21-year First Division title drought.
It may have taken Ferguson seven years to do so but he re-paid the club's faith tenfold by building what was the foundation of an ethos that would catapult United to the domination of English football.
Based on attack-minded tactics and commitment to youth, the Red Devils would win fourteen Premier League titles, six FA Cups, thirteen League Cups and two Champions League trophies while Ferguson was in charge.
It didn't work out for the Scot however as he was famously sacked after just ten months in charge with the club sitting seventh in the league.
In the following years, United would hire big name managers in Louis van Gaal and Jose Mourinho, who both delivered varying degrees of success but failed to win the Premier League or Champions League.
For an exciting prospect at the time such as James Weir, there was a noticeable shift within the inner sanctum at Carrington from the pre to post-Ferguson era.
The young midfielder signed his first professional contract under the former Scotland manager and would go on to make his United debut under van Gaal in 2016.
Asked about what it was like during the transition period at United, Weir told Tribalfootball.com: "It was strange because my first contract I signed was with Sir Alex Ferguson and then he left. The best way to describe it was that there was a lot of new people at the club. There is loads of people knocking around Carrington, I was only there for a brief time when (Ferguson) was there, but you knew everyone, it was like a family.
"David Moyes came in, [then] Van Gaal. And it was just more and more new people, a lot of changing of faces, and the family club started to diminish for me. Mainly I was with the reserves until van Gaal called me up for a couple of months, but you always hear rumblings from the first-team and it was an up and down period for the club."
Mourinho was sacked in December 2018 and replaced by United treble winner Ole Gunnar Solskjaer, who took over as a caretaker.
United would lose only once in 13 league games and Solskjaer was rewarded with a three-year contract in March 2019.
Although the club ended last season poorly, Solskjaer's side have improved this term and can move into third on the Premier League table if they beat Southampton on Monday, while they are also alive in the latter stages of the FA Cup and Europa League.
And Weir, who now plays for Slovakian side FK Pohronie, believes Solskjaer has restored the family atmosphere and has club is moving forward.
"Yeah definitely. I think when he went in there they were thinking is he a big enough manager to manage this club, but it's just the fact that he knew the club and getting that feel good factor back.
"And all the fans are on board and the players are on board so now it is going in the right direction, where it was going in the other direction."
To read our exclusive interview with Weir about his journey from United to Slovakia, click here.