Britain's Jamie Chadwick finished first after starting on pole position for the Indy NXT race at Road America to become the first woman to achieve success on a road course in the US racing series.
Chadwick, in the No 28 VEXT car of Andretti Global, claimed her maiden victory in the feeder series to IndyCar.
Chadwick had the race in full control but was forced to show her skill in a two-lap shootout at the end following a red flag.
Louis Foster, in second, and championship leader Jacob Abel could not find an answer as Chadwick created history.
"Oh man, I have no words," said Chadwick. "Honestly, [I'm] a bit emotional I think. We've had an unbelievable car this year and just haven't been able to really do anything about it so I'm just so happy we held on there.
"With the red flag at the end, I was like 'oh, come on', we started to lose the tyres a little bit. Louis had a look and I just knew I had to be aggressive. I know they have a championship to worry about and I just had to get my head down. I really wanted to win today."
Every driver on the track made a point of congratulating the popular British racer following her victory.
In May, the 26-year-old became the first woman to stand on the podium in Indy NXT when she took third place at Indianapolis.
Chadwick also launched a new initiative in an attempt to increase female participation in grassroots motorsport earlier this year.
The three-time W Series champion partnered with Daytona Motorsport in a year-long commitment to provide free karting and mentorship for girls.
She is the UK's most decorated active female motorsport driver, having dominated all three years of the W Series before crossing over to the fiercely competitive Indy NXT series.
Chadwick is also part of F1 team Williams' driver academy, and is taking on a mentoring role with their F1 representative Lia Block this season in F1 Academy.
Sunday June 9
6.05pm: Indy NXT
8.30pm: IndyCar Race
Sunday June 9
5.30pm: Grand Prix Sunday - Canadian GP build-up
7pm: THE CANADIAN GRAND PRIX
9pm: Chequered Flag - Canadian GP reaction
10pm: Ted's Notebook
Formula 1 is on Montreal for the Canadian Grand Prix this weekend live on SportNews F1, with Sunday's race at 7pm.
