U.S. Olympian Shalane Flanagan won the women's half marathon in 1 hour, 7 minutes, 51 seconds at the Rock 'n' Roll Marathon on Sunday, breaking her personal best by 40 seconds.
It was the second-fastest half marathon by an American this year, behind Molly Huddle's 1:07:41 at the NYC Half in March.
Amy Cragg, who beat Flanagan at the U.S. Olympic Trials marathon in February, finished two minutes behind Flanagan, but still ran a personal-best 1:09:51.
Rock 'n' Roll San Diego will be their only race prior to the Olympic marathon in August.
At the trials in Los Angeles, they ran together for the first 25 miles before splitting up when Flanagan started having trouble with the heat. Cragg won the race, with Flanagan finishing third.
The two have trained together this year, even going to Rio together in April to run on the Olympic marathon course.
On Sunday, they did their own thing.
"Amy and I have done some amazing workouts and we said, 'You know, let's see what we can do,' and we ran our own race today."
Eric Noel of San Luis Obispo won the men's marathon in 2:26:40 while McKale Davis of Chandler, Arizona, won the women's marathon in 2:56:16.