Peres Jepchirchir and Brigid Kosgei set the pace for most of Saturday's women's marathon, and the only question entering the final five kilometres was which Kenyan would cross the line first.
Jepchirchir finally broke from her countrywoman with a little over two kilometres to go and pulled away to win by 16 seconds.
Kosgei's second-place finish made Kenya the first nation to claim gold and silver in the event at the same Olympic Games.
“I pushed on the pace [and when I opened the gap] it was like, 'Wow, I’m going to make it. I’m going to win,'" Jepchirchir said.
"It feels good. I’m so, so happy because we win as Kenya. First and second. I thank my god so much. I'm happy for my family. I'm happy for my country, Kenya."
Ten seconds behind Kosgei, Molly Seidel of the USA shouted "Yes! Yes!" as she crossed the line for a stunning bronze medal in only her third competitive marathon.
Seidel is the third US woman to medal in the marathon, following Joan Benoit Samuelson's gold at the inaugural women's race in Los Angeles in 1984 and Deena Kastor's bronze at Athens 2004.
She said she took inspiration from her friend Courtney Frerichs' aggressive approach that led to a silver medal in the 3,000m steeplechase this week.
"Seeing her do that and race aggressively was truthfully what gave me the strength to not be afraid to stick my nose in it," Seidel said.
"It is just to go out, stick your nose where it doesn’t belong and try and make some people angry. My goal today was just to go in and for people to think, 'Who the hell is this girl?'."
ANOTHER GOLD FOR MCGEE FAMILY
JaVale McGee was a late addition to the USA basketball squad, but Saturday's victory over France made him a part of history.
McGee's mother Pam won gold with the USA in basketball at the 1984 Los Angeles Games, and she and JaVale are now the first American mother-son combo to win gold in any sport.
“It's an amazing feeling man," McGee said. "I got a gold medal, my mother's got a gold medal. You can't really explain it, just knowing you're the best in the world.
“If that don't add to the resume, I don't know what will. It's a family resume. That's what it’s all about, in the end, is family.”
YAFAI WINS BOXING GOLD FOR BRITAIN
Galal Yafai became the first British man to win boxing gold since London 2012, defeating Carlo Paalam of the Philippines for the flyweight title Saturday.
Yafai knocked down Paalam in the opening round and never looked back, winning 4-1.
The 28-year-old Birmingham native competed in Rio as a light flyweight but lost in the second round.
He is the first Brit to medal in the men's fly since 1956.
Paalam is the first man from the Philippines to medal in any sport since boxer Mansueto Velasco took silver in the light fly at Atlanta 1996.
BEACH VOLLEYBALL NEWCOMERS TAKE MEDALS
A sport traditionally dominated by Brazil and the USA saw three newcomers on the podium on Saturday.
The Norway duo of Anders Mol and Christian Sorum defeated Viacheslav Krasilnikov and Oleg Stoyanovskiy, representing the Russian Olympic Committee, to take home the gold medal.
In the bronze-medal match, Ahmed Tijan and Cherif Younousse of Qatar downed Edgar Tocs and 2012 bronze medallist Martins Plavins of Latvia.
None of the podium nations had won a medal of any kind in men's or women's beach volleyball before, though the winners do have an Olympic legacy of sorts.
Mol's mother, Merita Berntsen, placed ninth with partner Ragni Hestad in the first beach volleyball competition at the 1996 Atlanta Games, then retired when Anders was born the next year.
"My mum thought it was going to be really hard to travel around with two kids, because my brother was born in 1994. She had me and then quit," Mol said. "I always dreamed of beating my mum in the Olympics. She got a ninth [place[. I was actually really happy when we made it to the quarter-finals because we became historical by achieving [at least] a fifth place.
"It has been a journey for a long time and our parents and families are very proud of us right now."
SIXTH KAYAK GOLD FOR HUNGARY'S KOZAK
Danuta Kozak claimed her sixth Olympic gold medal as Hungary won the women's sprint kayak four 500 metres.
The 34-year-old teamed with Tamara Csipes, Anna Karasz and Dora Bodonyi to hold off Belarus and Poland.
It was Kozak's third consecutive gold in the fours after taking silver in the event in her Olympic debut in Beijing.
She also won gold in the K1 500m in London and Rio, and in the K2 in Rio. She took bronze in the K2 earlier this week, so Saturday's win gives her eight Olympic medals overall.
In other sprint kayak finals, Germany won the men's kayak four 500m, China took the women's canoe double 500m and Isaquias Queiroz dos Santos of Brazil won the canoe single 1000m.