CAPE ELIZABETH — As a foghorn blew softly behind her, Joan Benoit Samuelson shook her head at the passage of time since she helped give birth to the TD Beach to Beacon 10K road race, which turns 18 on Saturday.

“I don’t know where the years went so quickly,” Samuelson said as she looked over white tents that sprout annually on the lawn adjacent to the Portland Head Lighthouse. “But it certainly is an event that is well-supported on every front. Without that support, we wouldn’t have made it to 18.”

Joan Benoit Samuelson

Now 58, Samuelson was a bit sweaty from a morning 5-miler with a friend over the same roads she ran as a girl in Cape Elizabeth, a run that followed an earlier-morning 3-mile run in Portland with a race sponsor’s group. All that was on top of Tuesday’s 20-plus miles, which started with her own 16-miler in the morning (she’s training for the Chicago Marathon, after all) and concluded with another 5.5 miles that night around Portland’s Back Cove with a free training group.

“I started off in the back of the pack and I tried to catch the leader,” Samuelson said Wednesday morning, “so today I’m a little tired.”

So did you catch the leader?

“Close,” she said, “but I didn’t want to sprint because I didn’t want to set myself back with this.”

Never underestimate the competitive nature of an Olympic gold medalist, a woman who has been the face of American running since she burst into the national consciousness by winning the 1979 Boston Marathon as a Bowdoin College senior.

Her mother, Nancy Benoit, has often asked about the source of her daughter’s competitive streak. Some of it stems from growing up as the only girl among three brothers.

Much of it, however, runs in the genes.

“She was very ill this winter and has rebounded,” Samuelson said. “And I said, ‘You don’t have to look any further, Mom.’ ”

Although local favorite Ben True dropped out of the race Tuesday because of fatigue and a desire to rest for the upcoming world championships in China, Samuelson still had plenty to be excited about, including substantial prize money for the top five American men and women to reach the finish line.

“I think we’ve put a great field together,” Samuelson said, “a lot of local talent and regional talent and national talent. We’re still up against the world championships, so we’re not getting everybody, but we’re getting a lot.”

The race has a few new wrinkles this year, with race photos available at no charge to all participants and an opportunity to sign up for text notification of one’s finishing time immediately after crossing the line.

“We try to find something new and different and exciting every year,” she said. “You can’t rest on your laurels or become complacent with age.”

Samuelson and former race president David Weatherbie also said an athlete-driven seminar/informal run is planned for Friday at about 12:20 p.m., beginning at Cape Elizabeth High.

Local high school runners are invited to pick the brains of some of the American elites, including Alexi Pappas (a five-time All-American at Dartmouth and Oregon who won the Peachtree 10K earlier this month), Will Geoghegan (Brunswick native who also ran at Dartmouth and Oregon, and won last year’s Maine men’s category) and Riley Masters (Veazie native who ran at Maine and Oklahoma, and won the 2013 Maine men’s race).

This year’s race beneficiary will be the Good Shepherd Food-Bank.

“Great choice,” Samuelson said. “They serve people throughout the entire state of Maine and I think we’re building awareness for just how many food deserts there are in the state. … They’re going to be serving food at the Kids Race (Friday night) and they’ll have a presence at registration and the Expo. I’m very happy and the feedback has been very positive.”