Donald Trump took part in a ceremonial lap in his presidential limousine before waving a green flag to kick off a first-of-its-kind motor sports race through the streets of Washington DC.
The US capital's IndyCar race, one of a series that forms the top level of American car racing, was part of celebrations of the country's 250th anniversary.
American Kyle Kirkwood, driving for Andretti Global, gave the home crowd a victory to remember in the inaugural Freedom 250 Grand Prix on Sunday afternoon.
Denmark's Christian Lundgaard, driving for Arrow McLaren, came second, while Australian Will Power, Kirkwood's Andretti Global teammate, took third.
"This is incredible. I'm almost in tears here," Kirkwood told FOX. "That was a hard race."
Winding its way around the National Mall and Pennsylvania Avenue, the 1.7-mile street circuit provided a dramatic setting for a race that was expected to draw around 200,000 spectators.
Table leader Alex Palou arrived in Washington with six wins, but the four-time series champion suffered a setback when he received a drive-through penalty for making contact with a tyre after leaving his pit box under caution.
A slow pit stop later added to the Chip Ganassi Racing driver's problems.
The Spaniard fought back from 21st to seventh place, but his recovery ended with 25 laps remaining when he crashed into the wall at turn four, ending the race in 20th place.
Kirkwood, who pulled in front of Palou on lap two, retained control despite interruptions.
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Kirkwood's victory put him 91 points behind Palou. The next race will be in Milwaukee next week.
British driver Louis Foster came 18th.
Tickets were free for the race, in which drivers were expected to reach 185mph on the Pennsylvania Avenue straightaway, but passes to private trackside clubs sold for $5,000 (£3,664).
The track was originally set to run through the grounds of the US Capitol, but the proposal required lawmakers' approval and stalled in Congress.
The city's police shut major thoroughfares downtown due to pedestrian activity and security procedures.
The race is the latest in a series of sporting events Mr Trump has used to celebrate the country and his second term, as the US is embroiled in a war with Iran.
He opened the summer with a professional mixed martial arts bout on the South Lawn of the White House, then presented the World Cup trophy to champions Spain a month later.
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