Deena Kastor won her first race as a newly minted master on Sunday, claiming the women’s overall title at the Rock ’n’ Roll Pasadena Half Marathon. On a cool, clear, and windless Southern California morning, Kastor mastered the hilly, challenging course to finish in 1:12:57.

More than 7,000 runners participated in the half-marathon and accompanying 5-K—including celebrities Sean Astin, Joey McIntyre, Andrea Barber, and cast members from “Grey’s Anatomy”—but it was Kastor who stole the show. Spectators cheered her along a course that wound through tree-lined residential streets and the bustling commercial center of Old Pasadena, before finishing at Pasadena’s Rose Bowl.

Kastor split 10-K in 33:58 and was on pace through 9 miles to challenge Colleen De Reuck’s American masters record of 1:11:50, but the unrelenting procession of tough hills took its toll over the last few miles.

“Everyone seemed to be focused on me getting this masters record,” said Kastor, who turned 40 three days before the race, “but for me this was just perfect preparation for the Asics LA Marathon exactly one month from now.

“My legs feel like they do after a marathon,” continued Kastor, speaking about the course’s difficulty. “I might just jog a few miles tomorrow or take it off completely, because I definitely feel like this course took something out of me.”

Kastor’s victorious debut in the masters ranks marks a new milestone in a career that has spanned three decades. After winning her first national cross country race at age 12, Kastor was a five-time California high school state champion, 8-time All-American while running for the University of Arkansas, and multiple-time American open champion in cross country and track and on the roads. She holds nine American women’s road racing records, including the half-marathon (1:07:34) and marathon (2:19:36).

On Sunday, Kastor finished almost seven minutes ahead of the second woman, Mandy Grantz of Pasadena, who clocked 1:19:44. Kastor’s strong performance on a tough course should make her a favorite for the LA Marathon on March 17.

Adam Kovacs of Hungary won the men’s race in 1:06:42, with 2010 USA national marathon champion and defending Pasadena Half Marathon champion Sergio Reyes finishing third in 1:08:49.