For Sherry Missig, it’s been a long road to the starting line of the Boston Marathon. She’ll be there Monday morning, among the bobbing throng in Hopkinton town green, wearing bib number 26064.

Missig, 65, of Yarmouth, has been competing in road races for 37 years, debuting with a 10K in her native California.

But this will be her first Boston Marathon, after meeting the qualifying standard while running in the Mount Desert Island Marathon.

“I never thought I could qualify. I never dreamed I would ever come close,” she said.

Gary Allen, who directs the MDI Marathon and will be running his 24th Boston Marathon, calls Missig’s achievement extraordinary.

“Most people are thinking about getting a new recliner, not running Boston, at (her) age.”

Missig has run 13 marathons, the first in 1984 at the Marine Corps Marathon in Arlington, Virginia. Her time that day of 4 hours, 2 minutes remains a personal best. She has completed every marathon she has started, despite wanting “to quit at mile 8” during the Marine Corps Marathon one year. Missig also has run several marathons in Long Beach, California.

Missig and her husband, Mike, moved to Maine in 1991. During her 29-year career as a TWA flight attendant (she retired in 2000), she logged training miles throughout Europe and the United States. Her favorite local road races include the Yarmouth Clam Festival 5-miler, the L.L. Bean 10K and the Patriots Day 5-Miler in Portland.

For more than 20 years, she’s been training regularly with close friend Miranda Smith, a veterinarian at Bath-Brunswick Veterinary Associates.

Smith is a decade younger than Missig, but she acknowledged, “Sherry’s faster (than me), and always will be. She’s just been a really consistent runner for so long, and really just doing it for the experience, not with a goal of qualifying for Boston. So it’s really exciting that she has.”

Their regular runs go from near Missig’s house on Littlejohn Island, over the causeway and down Route 88 into Cumberland and Falmouth and back. Their shared marathons have become fairly regular, too – four MDI Marathons and the Bay of Fundy Marathon in 2013. Differently speeded, as one might say, they don’t race together.

But Missig’s sister, Kathy Heaps, often travels from California to compete in races with Sherry. Since 2007, the siblings have teamed to publish “The 2-Year Runner’s Journal,” a training log and reference guide.

Heaps and Missig ran in the MDI Marathon on Oct. 19, 2014. They ran the first 18 miles together before Heaps, five years younger, speeded up. She finished in 4:20:37, while Missig came in at 4:37:07.

It wasn’t until the car ride back, Missig remembers, that “the wheels in my head started turning … wait … I’m gonna be 65 in 2016, so …”

She needed a 4:40 to qualify for Boston. “I didn’t want to believe it. It couldn’t be true. Then I got really excited.”

Qualifying on the hilly, challenging MDI course is all the more reason to celebrate.

“Her efforts … show the resilience and dedication needed to toe the line in Hopkinton and to finish in Copley Square as a Boston Marathoner,” Allen said.

For good measure, Missig ran the Marine Corps Marathon again last fall, finishing in 4:33:48.

Heaps also met the Boston qualifying standard at the MDI Marathon. The sisters will be in Hopkinton on Monday.

“My stomach flips every time I think about the race,” Missig said. “I’m trying not to put pressure on myself,” she said. “I’d like to really enjoy it. My sister and I are planning to run Boston together, and take in the whole experience.”