English Premier League Roundup, May 14
Rooney drove home the spot kick in the 73rd minute after Javier Hernandez was fouled, ensuring that United overhauls Liverpool as the most successful team in English league history.
"Twenty years ago we were nowhere near Liverpool," said midfielder Ryan Giggs, who has played in each of United's 12 Premier League-winning teams since 1993. "It's great credit to the club, the manager and the players and it's a good feeling to be ahead of our greatest rivals."
Alex Ferguson's side needed only a point to regain the Premier League trophy from Chelsea with one game to spare, but the visitors fell behind after 20 minutes when Brett Emerton capitalized on poor defending and goalkeeping.
United's breakthrough came after a moment of controversy, when the striker Hernandez was tripped in the area by goalkeeper Paul Robinson.
Blackburn's players felt Hernandez went down too lightly, and the penalty was only awarded by referee Phil Dowd after he consulted his assistant amid protests from both teams.
Rooney kept his cool to score his 15th goal of the season.
"I was terrified, the ref took a long time to give it," Rooney said. "I had to compose myself. I'd been practicing all week."
The England forward, who grew up supporting Liverpool's local rival Everton, was 1 year old when Ferguson took charge at United in 1986. Ferguson later promised to knock all-conquering Liverpool "off their perch."
But by 1990 the Anfield club had raised the bar to 18 titles. United kept its faith in Ferguson and in 1993 he ended the club's 26-year wait for another league crown.
Eleven more have followed since then, and in that time Liverpool has failed to top the standings once.
"Top of the perch," read a banner raised aloft by United fans at Ewood Park.
United has an unassailable lead over second-place Chelsea, which is seven points behind with two games to play.
United overcame Chelsea's late resurgence thanks to its impervious form at Old Trafford where it has dropped points just once this season - a draw against West Bromwich Albion.
United can end the season with both the Premier League trophy and European Cup if it can overcome Barcelona at Wembley Stadium on May 28.