Dalilah Muhammad topped the world record time in the women's 400m hurdles final on Tuesday night.
But it wasn't enough for her to repeat as Olympic champion.
Sydney McLaughlin beat her own world record to win the highly anticipated race and secure her first Olympic medal.
McLaughlin took nearly half of a second off her previous world record (51.90 seconds) by finishing in 51.46. Muhammad, who won gold at the 2016 Rio Games, earned silver with a time of 51.58.
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Femke Bol of the Netherlands came in third at 52.03.
The other American in the final, Anna Cockrell, was disqualified due to a lane violation.
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McLaughlin set the previous world record time against Muhammad at the U.S. Olympic Trials in June and also posted a better time than Muhammad in the semifinal round in Tokyo.
The women's 400m hurdles final was similar to the men's final on Monday night. Norway's Karsten Warholm demolished his own world record, winning the race in 45.94 seconds for his first Olympic medal. American Rai Benjamin also beat Warholm's previous world record time while taking home silver.
