Man-of-the-match Yaya Toure was City's second-half matchwinner, seizing on a catastrophic blunder by Michael Carrick before finishing smartly past Edwin van der Sar.
Roberto Mancini's men just about deserved it too after surviving an early pummelling and two glorious opportunities for Dimitar Berbatov.
Their task was made easier when Scholes departed though, dismissed for a thigh-high studs-first lunge on Pablo Zabaleta. It means there will be no repeat of 1999 for United, who must concentrate on their bid for glory in the Premier League and Champions League.
City, watched by chairman Khaldoon al-Mubarak, have the chance to "change history" as Mancini has demanded, and will return to Wembley on May 14 to face either Bolton or Stoke looking to collect their first trophy in 35 years.
Unfortunately, firebrand Mario Balotelli threatened to put a dampener on celebrations when he unwisely rejoiced in front of the United fans, triggering a shoving match with Anderson and an angry reaction from Rio Ferdinand - who also squared up to City coach David Platt.
Source: PA
Source: PA