Many nonagenarians are happy if they can still tie their shoes. Harriette Thompson not only laced hers up, she smoked the competition at the Rock 'n' Roll San Diego Marathon Sunday.

The 91-year-old from Charlotte, N.C., finished the 26.2-mile course in a time of seven hours, seven minutes and 42 seconds, shattering the marathon distance record for 90- to 94-year-old women by more than an hour and a half. Her average pace was about 16 minutes a mile.

"I was tired at one point going up a hill and wasn't sure if I could finish, but then I felt fine," Thompson told ABC News today.

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Thompson said her legs are recovering pretty well today, especially considering she recently underwent nine rounds of radiation on them for cancer treatment. She raised more than $90,000 for the Leukemia and Lymphoma Society's Team in Training.

(Photo Credit: Brenny Thompson)

This was Thompson's 15th appearance in the Southern California race. She made her debut at the age of 76 in 1999. Treatment for oral cancer kept her out of last year's race. It also prevented her from training as much as she would have liked this year, although she managed to sneak in a 5K race just last weekend.

"She is an amazing woman though I'm not as surprised by her accomplishments as everyone else is " said son Brenny, 55, who ran the race with her.

Runner's World reported that Thompson is the second oldest woman to compete in a marathon, after 92-year old Gladys Burrill, who completed the Honolulu Marathon in 2010. Thompson was the only runner Sunday in her age category.

"We're seeing more and more people of all ages entering marathons as they discover that running is something that can keep you fit for a lifetime," said Tish Hamilton, the executive editor of Runner's World.

Thompson said she'll rest up for a few days and begin training again shortly.

"I hope to run the race next year even faster," she said, "if I'm still around."