First-time Olympian Simone Biles, 19, is the first U.S. gymnast to win four gold medals at a single Olympics. She's also the first American gymnast to ever win gold in vault. (AP Photo/Dmitri Lovetsky)

Prior to the 2016 Olympics, Puerto Rico had only won 2 silver and 6 bronze medals. Rising tennis star Mónica Puig changed that in Rio by winning the women's singles final and earning her country's first gold medal. (Photo by Clive Brunskill/Getty Images)

The Rio Olympics featured the first-ever refugee team, which used the Olympic flag as its own and included athletes from Syria, South Sudan, Congo, and Ethiopia. (AP Photo/Michael Sohn)

Self-proclaimed 'Shot Diva' Michelle Carter won the USA's first gold medal for shot put. She takes after her father, Michael Carter (right), who won silver in the same event at the 1984 Los Angeles Olympics. That fact also makes them the first father-daughter team in Olympic history to win individual event medals. (Reuters/Getty Images)

Gold medalist Simone Manuel's win at the 100-meter freestyle final made her the first female African American athlete to take home an individual medal in Olympic swimming. (Photo by Harry How/Getty Images)

Estonian sisters Lily, Liina, and Leila Luik are the first set of triplets to ever compete at an Olympic Games. The trio ran in the women's marathon event. (Photo by Buda Mendes/Getty Images)

Fiji scored its first-ever Olympic medal after competing in the Games since 1956. The island nations' rugby sevens team won gold by defeating Great Britain in the final. (REUTERS/Phil Noble)

Shooting champion Kim Rhode, 37, is the first sportswoman in history to medal in six consecutive Olympic Games. She has won three gold, one silver, and two bronze medals (her recent bronze from Rio is not pictured). (AP Photo/Jae C. Hong)

Kimia Alizadeh Zenoorin made history by becoming the first Iranian woman to ever win an Olympic medal. The 18-year-old earned a bronze medal for women’s 57kg taekwondo. (Photo by Laurence Griffiths/Getty Images)

Jamaica's own Usain Bolt became the first person ever to win gold medals in the 100-meter dash, 200-meter dash and 4 x 100m relay at three straight Olympics, aka the ‘triple-triple.’ (REUTERS/David Gray)

Fencing star Ibtihaj Muhammad is the first Muslim American athlete to compete at an Olympic Games while wearing a hijab. Muhammad earned a bronze medal in Rio for the women's team sabre event. (Photo by Tom Pennington/Getty Images)

British tennis star Andy Murray is now the first person to win consecutive Olympic gold medals in the singles tournament. He earned his first at the London 2012 Games and won again by defeating Juan Martín del Potro in Rio. (Photo by Clive Brunskill/Getty Images)

As the women's 4 x 100m medley relay team won their race, they were also racking up the 1,000th Summer Olympics gold medal for the USA, making it the first country in history to reach that milestone. (AP Photo/Rebecca Blackwell)

Jordan’s Ahmad Abughaush defeated Russia’s Alexei Denisenko to win taekwondo gold, his nation’s first Olympic medal since Jordan began competing in 1980. (Photo by Stanislav KrasilnikovTASS via Getty Images)

Texas native Connor Fields brought home Team USA’s first-ever Olympic gold medal in BMX cycling. (AP Photo/Patrick Semansky)

Japan's Kaori Icho became the first female athlete in any sport to win individual gold medals at four consecutive Olympic Games, thanks her victory in the 58kg freestyle wrestling event. She is also the first wrestler ever to win four Olympic gold medals. (REUTERS/Toru Hanai)

Egypt’s Sara Ahmed became not only the first woman from an Arab nation to win an Olympic weightlifting medal, but also Egypt’s first female medalist in the country’s 104-year-history in the Olympics (although another female Egyptian weightlifter earned a silver medal from the 2012 London Games retrospectively). (Photo by Julian Finney/Getty Images)

Joseph Schooling not only delivered Singapore its first-ever Olympic gold medal, but he did so by beating his idol Michael Phelps in the 100-meter butterfly. (AP Photo/Michael Sohn)

With Team USA’s win in the women’s 4 x 100m relay, Allyson Felix became the first woman in Olympic history to win five gold medals in track and field. Felix had previously won one gold at the 2008 Beijing Games and three at the 2012 London Olympics. (Photo by Cameron Spencer/Getty Images)

Serena and Venus Williams lost their first Olympic doubles match, after being knocked out in the first round in Rio. The sisters had previously gone 15-0, earning three gold medals together at the Sydney 2000, Beijing 2008, and London 2012 Games. (REUTERS/Toby Melville)

Kosovo made its debut as an Olympic nation at the 2016 Games, and already won its first gold medal thanks to judo champ Majlinda Kelmendi. (REUTERS/Toru Hanai/File Photo)

The U.S. became the first country ever to sweep the medals in the women's 100m hurdles event. Kristi Castlin (L) took home bronze, Nia Ali earned silver (R) and Brianna Rollins (C) won gold. (Photo by Cameron Spencer/Getty Images)

Hoàng Xuân Vinh scored Vietnam's first-ever Olympic gold medal by winning the men's 10-meter air rifle event in Rio. (Photo by Sam Greenwood/Getty Images)

The U.S. women’s 4 x 100-meter relay team ran the first-ever relay time trial at the Rio Olympics, after an impeded baton exchange allowed them to appeal and re-run the heat on their own. (AP Photo/Martin Meissner)

The Rio Games marked the first ever Olympic beach volleyball loss for Kerri Walsh Jennings, 38, ending her 26-match winning streak and preventing her from earning a fourth straight gold medal. Fortunately, Walsh Jennings and partner April Ross won their bronze medal match. (Photo by Jamie Squire/Getty Images)

Team GB's Max Whitlock made history by winning Britain's first gold medal in gymnastics, and he topped that by winning two events in the same day - floor exercise and pommel horse. (REUTERS/Marko Djurica)

Carolina Marin of Spain beat Indian favorite P. V. Sindhu to take home a gold medal in women’s singles badminton. It is the first time in Olympic history that a European country has won the event. (Photo by Clive Brunskill/Getty Images)