They won USA's first ever gold in cross-country skiing, as well as the first medal in the sport since 1976.
Jessica Diggins and Kikkan Randall of the United States (C) celebrate winning gold as they stand on the podium with athletes of Norway and Sweden.
Hamlin finished her Olympic career without a medal in Pyeongchang, but Diggins will undoubtedly make her country proud when she walks through the Olympic Stadium holding the American flag above her head.
Diggins was chosen by a vote from fellow members of Team USA.
"This is such an incredible honor for me", Diggins said in a Team USA release. It's so inspiring to feel the support and cheering from everyone.
The U.S. has 21 medals so far in and women have claimed 14 of them - 12 on their own, two others on mixed teams in figure skating.
Diggins is the first cross-country skier to be selected as the United States flag bearer for the closing ceremony.
PYEONGCHANG, South Korea (AP) - Jessie Diggins has one more big Olympic moment awaiting her.
On Wednesday, the 35-year-old and teammate Jessica Diggins took home the gold in the women's sprint free relay.
Much like the opening ceremony, the closing ceremony will feature all 91 countries (92 including Russia), with a flag bearer for each country.
"Jessie's breakthrough performances here in Pyeongchang have been inspirational and historic", U.S. Olympic Committee Chief Executive Scott Blackmun said.
Diggins held off the challenge of Sweden's Stina Nilsson in a furious sprint for the line to win gold and Norway's Marit Bjoergen became the most successful winter Olympian of all time with 14 medals after taking bronze with Maiken Caspersen Falla.