BEIJING — Kristin Armstrong won the gold medal Wednesday in the women's time trial, making her just the second American women's cyclist to become an Olympic champion.

Armstrong finished the 23.5-kilometer (14.6-mile) course in 34 minutes, 51.72 seconds — 24.29 seconds better than Emma Pooley of Britain. Karin Thuerig of Switzerland was third, almost a minute behind Armstrong.

Pooley was the fifth of 25 riders down the ramp, setting a time that let the other contenders know what they needed.

Armstrong was the only woman close to Pooley at the halfway mark, and erased the gap before reaching the finish at the Great Wall. She joins Connie Carpenter-Phinney as the only American women to win Olympic cycling gold. Carpenter won the road race at Los Angeles 24 years ago.