Simon Pagenaud clinched the IndyCar title on Sunday with a dominant victory in the Grand Prix of Sonoma.
Team Penske driver Pagenuad, who went into the final race of the campaign with a 44-point lead over team-mate Will Power, began from pole and controlled the race from start to finish to claim his fifth victory of the year and maiden IndyCar title.
Australian Power's challenge was ended by a gearbox failure 37 laps into the 85-lap race.
The 2013 champion was second at the time but had been towed into the pits before emerging five laps down on Pagenaud.
He eventually finished in 20th, eight laps off the pace, with Graham Rahal (Rahal Letterman Lanigan Racing) second ahead of Juan-Pablo Montoya (Team Penske).
Describing his feelings afterwards, Pagenaud said: "Unbelievable. There's so much emotion. My whole career has been about today, about getting to this level.
"To perform to 100 per cent with this pressure, it's amazing."
Meanwhile Power was left to rue his mechanical problems, saying: "It's unfortunate for us we didn't have a shot today.
"It's just how it flows. When it's your year, it's your year. He earned it. Simon did a phenomenal job. I was happy to see him win a championship even though I finished second."