The 17-year-old, who has melted the hearts of home fans in Pyeongchang thanks to her ever-ready smile and Korean heritage, justified her status as the hot favorite with an eye-popping top score of 98.25.
Jiayu then washed out on her last trip down the longest Olympic halfpipe since the sport made its debut in 1998, turning Kim's last run into a victory lap.
Even though Chloe didn't need to prove anything in the third round of competition, she went full-throttle and pulled off a near-perfect run.
Kim has said she often cries when speaking about her father, the man who is the embodiment of the American Dream, emigrating to the States in 1982 with $800 in cash. He also said she embarrassed him once at a local skate park because she was that good.
Kim has been projected to win this event by a wide margin for years, but U.S. Olympic history has enough seemingly sure-things who never quite closed the deal for today still to be celebrated. She was glum after the second and jubilant following the third run in which the crowd gasped at every trick.
"I knew that I wasn't going to feel as satisfied if I didn't land that". She didn't have an Olympic gold medal and she had a respectable number of followers on Twitter, but nothing especially jaw- dropping. "This one's for Grams", Kim said.
But nope! Chloe Kim did not take it easy.
Her father, Jong Jin, quit his job as an engineer over ten years ago to focus on helping his daughter hone her craft.
Who is leading the overall medal count?
- Speed skater Bonnie Blair is tied with Heiden for most total gold medals in the Winter Olympics, with five.
"I'd say do whatever you want", Kim said.
She was well ahead of silver medalist Liu Jiayu of China, who earned 89.75 points and Arielle Gold of the US who took bronze with 85.75.
Chloe Kim stamped her name on a new era of snowboarding with a run down the halfpipe that, officially, did not mean anything. She was 11 years and 302 days old.
While she was training for the Olympics, she turned to pizza.
"I was in the lift line at Mammoth, and this little girl in a blue helmet with a pink face mask asked to ride the chair with me", Olympic snowboarder Kelly Clark told ESPN. "But at the end of the day, I'm here - and I'm so happy". She has won big on the World Cup circuit, and at the X Games.
But the serious business of chasing a gold medal took an emotional toll.
Nike, Toyota, and Visa are among companies that already sponsor Kim, and her marketing appeal is set to explode.
Kim's parents bought her first snowboard on eBay for just $25. But the weather cooperated, with a clear and sunny sky, moderately cold temperature, and light winds.