The US women confidently collected their third straight 4x400m title, dominating the proceedings from gun to tape on a wet and windy evening at Thomas A Robinson Stadium.
Phyllis Francis led off with a solid 50.42 opening lap – the fastest of the race – to hand Ashley Spencer a 1.13-second lead. The Olympic 400m hurdles bronze medallist immediately went to work, piecing together a lead of some 10 metres by the end of her sub-51-second circuit.
Quanera Hayes was next and like the world 400m leader did in the heats on Saturday, she simply put the race well out of reach with her 50.66 leg, nearly doubling the quartet's lead to more than 15 metres after three laps.
There was little pressure on Natasha Hastings on anchor who nonetheless padded the lead before crossing the line in 3:24.36, a world lead.
"I did have some ceviche and boiled plantain this morning so maybe that helped," Hastings joked. "But on a serious note, I'm specially blessed to have this group of young ladies with me."
Well behind her, a fierce battle ensued over the final lap for the remaining podium positions. Poland's Justyna Swiety won that one, clawing her way from fourth midway through the final turn, to second, just nipping Jamaican Stephenie Ann McPherson a couple steps from the finish to secure her country's first World Relays medal in the event. Poland clocked 3:28.28 to Jamaica's 3:28.49.
"I'm really surprised for how this race went for me," said Swiety, a bronze medallist in the 400m at last month's European Indoor Championships. "Hopefully (at the World Championships) in London it will be even better."
In a fairly tight finish, Great Britain and Northern Ireland were fourth in 3:28.72, with Botswana sixth (3:30.13).
Nigeria (3:32.94) in seventh and France (3:35.03) in eighth also secured their automatic qualifying spots for this summer's IAAF World Championships London 2017.
Bob Ramsak for the IAAF