Mike Lowell, named the Most Valuable Player in the final, and pinch-hitter Bobby Kielty each hit solo home runs to spark the Red Sox to a 4-3 win in Denver.

"I'm on Cloud Nine," Lowell said. "It's unbelievable. A lot of people expect you to win a world championship. For us to come through and do what we thought we were capable of, it's unbelievable."

After an 86-year gap between Series titles before a drought-snapping 2004 sweep of the St Louis Cardinals, the Red Sox's devoted supporters suffered only a three-year delay until the latest victory.

Boston's arch-rivals, the New York Yankees, and the Cincinnati Reds are the only other clubs who have recorded two sweeps in a row in World Series appearances. The Yankees, St Louis and the Oakland Athletics are the only clubs with more titles.

Lowell, now a free agent third baseman since his contract expired with the season, blasted his home run in the seventh inning off Colorado's Aaron Cook to give Boston a 3-0 lead. "I got my hands inside and I knew I hit it well," Lowell said. "It was a great feeling."

After Colorado's Brad Hawpe answered with a solo home run, Kielty smacked his blast on the first pitch of the eighth inning. Colorado's title hopes, once as lofty as their high-altitude mountain home, had seemingly vanished into thin air.

However, the Rockies refused to quit, with Garrett Atkins belting a two-run homer off Hideki Okajima, the Red Sox relief pitcher, in the eighth to pull Colorado within the final margin.

That set the stage for Jonathan Papelbon, Boston's closer, who entered the game to force the final five outs.

Colorado's Jamey Carroll blasted the ball deep to left field in the ninth inning but it was caught for the penultimate out.

"I couldn't breathe in the last inning," Terry Francona, the Red Sox manager, said. "You were fighting so hard to get through the game. So many guys had to dig deep. It's so hard."

Seth Smith, the Colorado pinch-hitter, followed by striking out, touching off a huge victory celebration on the field by the Red Sox.

"It's just phenomenal," Papelbon said. "We did everything we could to keep the lead. It took all 25 of us to get the job done."

It was a humble end for a Colorado club that made landmark late-season strides simply to reach its first World Series, winning 21 of 22 games before being swept. The Rockies won 13 of their last 14 regular-season games, a one-game showdown with San Diego for the last play-off spot and seven in a row in the National League playoffs.

But an eight-day layoff before the Series began hurt, a wait during which the Red Sox made an epic rally to reach the Series much as in 2004. Boston trailed Cleveland 3-1 in the American League final but won the last three games to reach the Series. In 2004 the Red Sox fell behind the Yankees 3-0 but became the only team in history to rally from such a hole to advance.

"What happened in '04, I will never forget it," Francona said. "But this is '07 and we said that from day one. And we accomplished our goal. It's not easy. When you see players you rely on go through the ups and downs, it makes it really special."

Boston's power-packed $143 million-dollar line-up was the second-costliest in the sport while Colorado's $54 million payroll ranked 25th of 30 clubs.

The Red Sox's dominant pitching, a trademark throughout the season, sealed the hosts' fate in the decider. Colorado batted only .218 in the Series.

Jon Lester, who missed most of the season after treatment for lymphoma cancer, threw five and two-third shutout innings, striking out three and giving up only three hits to remain unbeaten over 15 starts since August, 2006.

"I'm so proud of Jon," Francona said. "The way he pitched, the way he composed himself, the way he competed - it was very appropriate he got the win."