The Canadian pair were trailing 0.23 seconds after the previous day’s first two runs at the Sanki Sliding Centre, but they then delivered two more consistent bursts to clock a combined time of 3 minute 50.61 seconds, finishing 0.1 second ahead of the second-placed USA-1 team. The USA-2 team of Jamie Greubel and Aja Evans won bronze with a time of 3 minutes 51.61 seconds.
“It's really hard to describe my feelings,” said an emotional Humphries, who was keen to pay tribute to the role played by her friends, family and team-mates.
“Sacrifices have been made not only by myself but also my friends, my family. And then Heather has come on board. It's just something we have done together. And it's great.”
Meanwhile, Williams, who won a silver medal in the women’s 100m at the 2004 Olympic Games in Athens, and more recently was a member of the US 100m relay squad that won gold at London 2012, had completed a successful switch to bobsleigh, serving as brakewoman on the USA-1 sled, piloted by Elana Meyers.
She becomes just the fifth athlete in history, and the third woman to win medals in both the Summer and Winter Games.
The only other athletes to that feat were: Eddie Eagan of the USA, who won a gold in the boxing at the 1920 Summer Games and another in the four-man bobsleigh at the 1932 Winter Games; Jacob Tullin Thams (NOR) who won ski jumping gold in 1924 and yachting silver in 1936; and Christa Luding-Rothenburger (GDR), who won multiple speed skating medals in 1984, 1988 and 1992, to go with a sprint cycling silver in 1988; and Clara Hughes (CAN) who won bronze medals in the road race and time trial in 1996, before claiming another bronze in the 5,000 m speed skating bronze in 2002.
“It's really cool to be here, to be on a podium and to get that silver medal,” said Williams, who was keen to deflect attention from her personal achievement.
“I came here not to make history but to help the USA. And I feel like I did the best I could for it and I'm really excited with our performance and we're happy to be here.”
Meyers and Williams, who led by 0.23 seconds after first two runs, looked to be in with a real chance of gold, but errors on the second day of competition proved costly.
And Meyers was left ruing some missed chances. “Many times we were so close and we could taste it,” she reflected.
“It hurts a little bit. But at the end of the day I'm super-relieved with this medal. I have to deal with this to go back and train even harder for Pyeongchang.”
Meanwhile, Greubel, the pilot of the USA-2 team, was thrilled to win bronze.
“If you've asked me four years ago if I'd be an Olympic medallist I don't think I would believe you,” she said.
“But to cross the finish line and to know that we did it together, it's such an incredible feeling.”