The Irons won for the first time in 18 years at United thanks to goals from Tomas Soucek and Jarrod Bowen.
After the 2-0 win, Potter said: "Winning away at Old Trafford, I don’t think it happens too often for West Ham, so it’s a fantastic day for everybody connected with the Club.
"I’m so pleased for the players and the supporters. You know, we’ve had a tough season, so to give the supporters, who’ve been fantastic with us, that type of day, I think it’s really important for everybody connected with the Club, as the support we’ve had has been amazing.
"It’s been a tough couple of months, to be honest. Results-wise, the performances have been quite good and getting there.
"I think today’s just a nice reward for everybody because sticking together and being connected is not easy when results don’t go your way.
"So, yes, I’m just really proud of the players."
Playing the way we want
Potter felt the win and the manner of their goals showed the team is now improving and making progress under his management.
He contined: "We scored two goals goals today, and I think we scored some good goals at Brighton and the goal we scored against Tottenham was a good goal, too.
"We’ve had some good passages of play, but the hardest thing in football is attacking, to create, to be the protagonist in the game.
"We’ve had to suffer a little bit on the way because we’ve inherited a situation where the team was conceding a lot of goals, and we’ve tried to address that and then you sort of move on towards how we want to be.
"We’re a long way from where we want to be, but I think there are signs.
"I can’t fault the players. Like I said, the biggest thing I can say to them is it’s not easy when you go on a run like we’ve had and to be connected, to be together, to be fighting for each other, to work every day in the best way, I think it’s a credit to them.
"Credit to them as professionals, as they’ve been fantastic."
A brilliant day
Potter was also keen to highlight the unity between the players and the away support on the day.
He added, "When you win at Old Trafford, I think you have to have everybody doing everything as best they can, and I think that was the case.
"You need the subs to come on, you need the starting players to be good, your goalkeeper to make some saves, defenders to defend when they have to, midfielders doing both, forwards helping out, everything.
"You need everything, to score some good goals, to suffer when you have to, collectively.
"You need everything, and our supporters were there as well, so it was a brilliant day."