Lilly King won the 50 metres breaststroke in a 2017-best and US record time of 29.66 seconds, while Justin Ress swam the year's fastest men’s 50m backstroke, winning in 24.41 to represent the US at next month's Budapest world championships.
King added the 50m national title to her triumph in the 200m race on Wednesday.
“It’s awesome," said Olympic 100m breaststroke champion King, who also won the 200m race on Wednesday. "The 50 (breast) is just a splash and dash, so I get in and go literally as hard as I can. It was fun tonight.
"I’m always happy to get the American record, and it was great to get that tonight, but I was hoping to be a little bit faster and hopefully get the world record. But I’ve still got a little bit left in the tank for Budapest.”
Ress broke the national championships record to win his first US title.