lead the women's Omnium cycling event at the London Olympics entering today's final event of the six-event competition.
But she had to settle for a silver medal on the podium, after Great Britain's Laura Trott finished one point ahead of her.
Taking the final place on the podium was Australia's Annette Edmondson.
Going into the race today, Hammer added a point to her lead over Laura Trott of Great Britain by finishing second in the 10-kilometer scratch race at the Velodrome at London's Olympic Park behind Annette Edmonson of Australia while Trott was third. In a scratch race, the winner is the first to cross the finish line.
As of this morning, Hammer has 15 points in the two-day, six-event competition, two fewer than Trott.
In each event, the winner receives one point, the second-place rider two points and so on. The rider with the lowest total score is the winner.
The omnium concluded with a 500-meter time trial where each rider sought the fastest time.
Hammer began today's competition by winning the individual pursuit event, completing the 3,000 meters in 3 minutes, 29.554 seconds, nearly 31 mph. Trott was second in 3:30.547.
In the individual pursuit, two riders start at opposite sides of the track and race against the clock. Individual pursuit is Hammer's best event in the omnium. She was fifth in the 2008 Olympics in the individual pursuit race, which was not included in the 2012 program.
Hammer and Trott both had 12 points entering the individual pursuit, but Trott was the leader because she won two events.
Hammer was fifth in Monday's opening event, the flying lap 250-meter time trial in 14.369 seconds, while Trott won in 14.057.
Hammer was also fifth in the 20-kilometer points race with 25 points, while Trott was 10th with 14 points. Malgorzata Wojtyra of Poland won with 34 points. Riders score points for sprints that occur every 10 laps around the 250- meter track and for lapping the field.
The first day of the event ended with Trott overtaking Hammer on the back straightaway of the final lap to win an elimination race, a bunch race with an intermediate sprint every two laps with the last rider each time eliminated. Hammer held on to finish second.
"Today, everything worked out well," the 28-year-old Hammer said Monday. "I'm very happy with the way I executed, being focused on each and every start."
Hammer, who graduated from Chaparral High School in 2000, won a silver medal in the omnium in the 2011 UCI Track World Championships and won the event at the 2012 London Olympic Test Event.
Hammer retired from cycling in 2003 but was inspired to return to the sport after watching the 2004 Olympics on television.
Hammer was part of the four-member U.S. team that won the silver medal in the team pursuit Saturday. --City News contributed to this report.