Gerard, 17, also became the youngest United States men's Olympic champion since 1928 with his victory in slopestyle, with Canada's Max Parrot taking the silver. He was in 11th place heading into his third run, but he executed it perfectly, essentially doubling his score with an 87.16, which was good enough to beat Canadian Mark McMorris, who was leading with 85.20.
Red Gerard poses on the podium after the snowboarding men's slopestyle finals at the Olympic Winter Games PyeongChang 2018 on February 11, 2018 in PyeongChang, South Korea.
Gerard is the second straight American to win slopestyle snowboarding, which made its Olympic debut four years ago.
Gerard had not won the gold medal yet - the event's three favorites were still to come. Samuel Girard of Ferland-et-Boilleau, Que., finished fourth in the men's 1,500-metre short-track speedskating event, a solid result for the Olympic rookie.
This was not the first time an American gold medal performance on NBC was spoiled. It was one of the highest-scoring rail sections of the day. The siblings danced to a medley of Perez Prado songs.
The Canadians were fully aware of all the medal possibilities in slopestyle, saying as far back as Monday, right after they got their first look at the Phoenix Snow Park course, that all four of them had medal potential on it. First Olympics and to make it on the podium?
"I don't know why I smile so much", Biney told USA TODAY Sports in a recent interview.
"I didn't have a flat race and wanted to have a flat race and didn't happen".
"I'm going to get a few more rotations hopefully at practice and step up the rail line a bit", McMorris said after the heats.
Biney was born in Ghana and moved to the U.S.as a 5-year-old.
Gerard had to recover from a poor start to the Men's Slopestyle final, but stomped his final run.
The teenage snowboarder said past year that he didn't really think about the Olympics.
Earlier Sunday, strong winds forced the postponement of the showpiece men's downhill alpine skiing race, and a shallow 4.6 magnitude natural disaster jolted parts of eastern South Korea. We will continue to update the official medal count throughout these 2018 Winter Olympics.
In mixed doubles curling, Winnipeg's Lawes and Ottawa's Morris continued their tear through the round-robin, thumping Switzerland 7-2 before routing the Olympic Athletes from Russian Federation 8-2 to improve to 5-1.