Derided since their formation a decade ago as an artificial "franchise" club, the League One (third tier) side caused widespread delight by inflicting a humiliating 4-0 defeat on Louis van Gaal's supposedly mighty Manchester United.
It came on the day that United, English champions 13 times in the last 22 years, paid a British record transfer fee of almost sixty million pounds ($99.40 million) for Real Madrid's Angel di Maria.
Van Gaal, who has yet to win in three competitive matches for his new club, may have made ten changes for the game, but nobody in Milton Keynes, 45 miles north-west of London, was allowing that to detract from the greatest day in the history of the football club - and arguably the town itself.
Developed from a small village in the 1960s, with the aim of becoming a major regional centre, Milton Keynes had been best known until a decade ago for its roundabouts and iconic sculpture of concrete cows.
Then in 2003 Wimbledon football club, FA Cup winners 15 years earlier, were moved there from south London by their owners against the wishes of most supporters.
The following year the name was changed to MK Dons, while dissenting fans formed their own club, AFC Wimbledon, who subsequently reached the Football League.
Bad feeling remains between the two, who have subsequently met twice in cup matches. The most recent occasion was a fortnight ago in the first round of the Capital One Cup, when a 3-1 victory earned MK Dons their glamour tie against United.
By winning it in such convincing fashion on Tuesday night, in front of a record attendance of 26,969, they hope to have thrown off the mantle of unpopularity in which they have always been shrouded.
"It's the day we came of age," the club's owner and chairman Pete Winkelman, a former music executive, told BBC Radio on Wednesday.
"We're a young club with lots of controversy in the beginning and we're proud to be making history at last."
Asked if it would lead to greater acceptance within football, he said: "I hope that it will allow the club to look forward.
"Since the club's been in Milton Keynes it's made a real difference locally."
Although the club have never played above the third tier, Winkelman has greater ambitions. "I've no doubt that one day Milton Keynes Dons will be a Premier League football team," he said.
"But whatever happens, that result will never be forgotten in Milton Keynes.