Valarie Allman of the United States' opening throw of 68.98m was enough for her to hold onto Olympic gold in the women's discus at the Olympic Stadium.
The 26-year-old had come into Tokyo 2020 among the favourites after a season's best of 70.01m at the U.S Trials.
“I am so honoured that this has been a first gold medal in Tokyo (for the USA in athletics)," Allman said after her victory. "It is an honour, I couldn't be any happier or more proud.
"I’m still waiting for my feet to touch the ground.
"Our team is filled with so many incredible athletes, and I am just blown away that I am not only a medallist, I am the gold medallist. It is like a dream come true.”
While the rain put a halt to competition halfway through, the field events inside the Olympic Stadium eventually resumed but none of Allman's fellow competitors was able to come close to her mark.
The Team USA athlete had failed her second and third attempts but her fifth attempt recorded 66.87m, which became the third-longest throw of the evening.
Kristin Pudenz of Germany won silver (66.86m) and Cuba's Yaime Perez came away with the bronze (65.72m).
For Perez, who recorded no marking five years ago at the Rio 2016 Games, clinching the bronze medal was a great feeling.
"It is a lot of years worth of work and the only medal that was missing (from my collection) was this one. Like every other athlete I wanted gold, but I’m happy with what I’ve got,” she said.
Sandra Perkovic of Croatia was looking to become the first athlete to win the women's discus throw three times at the Olympic Games but had to settle for fourth.