The 22-year-old took the lead early and never gave her opponents a chance, clinching her spot in the world championships in front of an adoring crowd.
"I was just gonna finish the race, knew anything was possible," she said.
Britton Wilson finished 1.67 seconds behind with Shamier Little taking third in 53.92.
McLaughlin previously set the record with a 51.90-seconds performance at the U.S. Olympic trials a year ago, only to shatter that figure in Tokyo, collecting gold in 51.46.
