Sanya Richards-Ross' quest for gold in the women's 400-meter began Friday, as the American runner moved into the semifinal round on the first day of track and field at Olympic Stadium.
The Jamaican-born Richards-Ross had the 12th-best time in the opening round of the event. Amantle Montsho of Botswana had the best performance with a run of 50.40 seconds, 1.38 ticks faster than Richards-Ross.
Richards-Ross, who is married to Jacksonville Jaguars defensive back Aaron Ross, earned bronze in the 400 four years ago in Beijing. She is trying to become the first women from the United States to win gold in the event since Valerie Brisco-Hooks did so at the 1984 Los Angeles Games.
In addition to Richards-Ross, Francena McCorory and DeeDee Trotter of the U.S. also earned places in Saturday's semifinals. McCorory had the third-fastest time at 50.78 seconds and Trotter was just .09 seconds further back in fifth.
Great Britain's Christine Ohuruogu, the 2008 gold medalist, was fourth.
The U.S. also placed three throwers in Friday night's 12-man shot put final. Reese Hoffa topped the qualification round with a throw of 21.36 meters, while Ryan Whiting and Christian Cantwell, the silver medalist in Beijing, finished fourth and ninth, respectively.
Angelo Taylor, Kerron Clement and Michael Tinsley of the U.S. all moved into the semifinals of the men's 400m hurdles. Taylor won gold in Beijing and Clement claimed silver.
Friday morning also marked the start of the women's heptathlon and there were also qualifications in the men's hammer throw and 3,000m steeplechase.
In addition to the shot put finals, medals will also be awarded for the women's 10,000m race. There will also be seven heats in the women's 100m, including separate ones featuring favorites Veronica Campbell-Brown of Jamaica and Allyson Felix of the U.S.