Australia's McKeon triumphed in the women's 100 metres butterfly first, recording a time of 55.91sec. at the American city's LISD Westside Aquatic Center.

America's Kendyl Stewart of LA Current finished second in 56.69, while London Roar was represented on the podium again through France's Marie Wattel, third in 56.76.

McKeon's second victory came in the 200m freestyle in 1:53.58, beating Australia's Madison Wilson of NY Breakers in 1:54.91 and Veronika Andrusenko of Iron in 1:54.99.

Fellow Australian Atherton won the women's 50m backstroke, finishing in 25.99.

LA Current's Beryl Gastaldello, from France, was second with a time of 26.13 and another Australian, Holly Barratt of London Roar, came third in 26.41.

Atherton then topped the podium in the 200m backstroke, securing a winning time of 2:00.58.

She was followed by America's Kathleen Baker of LA Current in 2:03.06 and Katinka Hosszú of Iron in 2:04.07.

The success of the Australian duo helped London Roar top the standings with 253.0 points, with the team winning 10 races across the day in total.

This included the women's 4x100m free relay and men's 4x100 medley relay, which scored double points. 

It’s been fantastic,” said London Roar coach Peter Bishop. 

"So impressed with the team. 

"So impressed with the start we’ve got here. 

"It’s only day one though, another big day coming tomorrow."

LA Current are the second-placed team with 234.0, while Iron are third on 186.0 and NY Breakers fourth on 131.0. 

Atherton and McKeon are currently second and third in the race for match most valuable player, awarded to the top scorer at the conclusion of day two, with 22.5 and 21.5 points respectively. 

Russia's Vladimir Morozov of Iron leads with 23 points.