Athing Mu of Team USA competes in the 800-meter final at the World Athletics Championships in Eugene, Oregon. (Sam Barnes/Sportsfile via Getty Images)

The final day of the World Athletics Championships in Eugene, Oregon, brought plenty of thrilling finishes as the United States continued to add to its medal haul on home soil.

Olympic champion Athing Mu headlined the United States’ productive Sunday, capturing the 800-meter title by eight-hundredths of a second. Holding off a challenge from Britain’s Keely Hodgkinson down the stretch, Mu finished with a time of 1 minute, 56.30 seconds, the fastest so far this year.

At 20 years old, Mu is now the youngest woman in history to hold Olympic and world titles in an individual track and field event. She also is the first American woman to win the 800 at worlds.

“At the end of the race, golly, I was just happy it was over,” Mu said after the race. “Today was kind of a rough day for me. I was just happy I could make it to the line and finish the race. Thank God I won gold.”

The United States also topped the podium in the 4×400-meter relay, delivering America its record 33rd medal of the competition.

Sydney McLaughlin, the 400-meter hurdles world champion, anchored the relay team, which also included Talitha Diggs, Abby Steiner and Britton Wilson, securing the United States a comfortable 2.93-second win over Jamaica. The 22-year-old’s staggering 47.91 split delivered the 4×400 relay team a dominant three-minute, 17.79-second finish.

Sunday’s win marks the United States’ fifth straight Olympic or Worlds gold medal in the 4×400 relay event. The first-place finish also secured Allyson Felix, who briefly returned from her recent retirement to run in the event’s preliminary race, a record-extending 20th career world championships medal.

“We’re a family, we stick together,” McLaughlin said after the 4×400 relay final. “Allyson came out of retirement to get us here, so we wanted to do this.”