Josef Newgarden won the 2017 IndyCar championship on Sunday with a runner-up finish to French Penske teammate Simon Pagenaud in the season finale at Sonoma, California.
The 26-year-old American started from pole after clocking a track record in qualifying on Saturday.
The point he gained for the pole saw him stretch his lead atop the standings to four points over New Zealand's Scott Dixon going into Sunday's race, which was worth double points.
Newgarden drove seamlessly from pole, leading 41 laps of the 85-lap race on the 2.385-mile (3.84 Km) Sonoma Raceway.
But 2016 series champion Pagenaud's aggression -- he twice missed the chicane at turn nine, kicking up dirt as he drove through the grass -- and his bold strategy of four pit stops proved the difference.
"We did what we had to do," Pagenaud said. "We tried. We won the race. It wasn't enough."
Pagenaud emerged from his late final stop ahead of Newgarden, who couldn't find a way past, finishing 1.0986 behind Pagenaud -- but 13 points ahead of him in the final season standings.
Australia's Will Power gave Penske a podium sweep and Chip Ganassi Racing's Dixon finished fourth -- and third in the title chase, 21 points behind Newgarden.
"This is unbelievable, a dream come true, and it took so much to get here," said an emotional Newgarden, in his first year with Penske after driving early in his career in Europe and Indy Lights before landing rides with IndyCar outfits owned by Sarah Fisher, Wink Hartman and Ed Carpenter.
"I almost don't know what to say."
Newgarden became the third Penske driver in four years to win the title after Power in 2014 and Pagenaud last year.
Newgarden also became only the second US-born champion since Sam Hornish in 2006. The other was Ryan Hunter-Reay in 2012.
"This means so much to me and the sport," said Newgarden, a US flag draped over his shoulders. "To finally get it done is a dream come true."
Pagenaud said having a homegrown champion was good for the series.
"Having an American champion is really important in this sport," the Frenchman said "and Josef will be a great champion."