BOSTON — Inside a church off the Hopkinton town green Monday morning, Joan Benoit Samuelson encountered Falmouth’s Sheri Piers, who was preparing to run her first Boston Marathon as a masters competitor in what promised to be record-breaking heat.

“Sheri,” Samuelson said. “You could win this whole thing for the U.S.”

Piers smiled.

Twenty-six miles later, she was still smiling. Only this time Piers was basking in the cheers of sun-splashed spectators along flag-draped Boylston Street as the first American across the finish line in the 116th edition of the Boston Marathon.

Piers, 40, was the second female masters runner and 10th woman overall, earning prize money totaling $9,200.

“This is my kind of weather,” Piers said of the unusual warmth that climbed into the upper 80s on the storied 26.2-mile course stretching from Hopkinton to Copley Square. “My plan (Monday) was to not even worry about my watch … I was just trying to run for place and catch as many people as I could.”

Coming off a lousy half marathon last month in New York City during which she made three bathroom breaks and finished 44th in a little over an hour and 23 minutes, Piers cast aside all thoughts of running fast Monday and focused instead on running smart.

She passed the half marathon mark in just under 1:20, slower than her usual pace but still within three minutes of an elite pack of nine women that eased through in a pedestrian 1:17.

With training partner Kristin Barry of Scarborough and Barry’s father relaying information to Piers at various points along the course, Piers was able to work her way up through a wilting field.

“They’re dropping out,” Barry would call out. “You’re in 13th place. You look great!”

Piers said she saw Barry four or five times along the course and got a boost from every encounter. Piers also said she dumped water on herself at every opportunity because she doesn’t sweat all that much.

“It definitely took away from the time,” she said, “but I needed to do it.”

Because the elite women started half an hour before the rest of the field, Piers ran much of the race alone and stayed ahead of the top men until Mile 25. Men’s champion Wesley Korir of Kenya was being fitted for a laurel wreath when Piers strode down a boisterous Boylston Street to finish in 2:41:55, a little over a minute behind masters champion Svetlana Pretot of France and 10 minutes behind women’s winner Sharon Cherop of Kenya.

“It gave me chills,” Piers said of the frenzied final few blocks. “I couldn’t wait to be done.”

The last time a Mainer was the first male or female across the line at Boston was 2006, the second of two successive such races for Emily LeVan, formerly of Wiscasset and now living in Vermont.

A year ago, Piers finished in 2:39 and grumbled about it being slower than her 2009 time and coming one month shy of her 40th birthday, meaning she missed out on third-place prize money ($2,500) in the masters division.

This year? Slower time and wider smile.

“I felt great,” she said. “It’s rare when it happens, but you almost feel like you’re running on water.”

Nick Wheeler, a 2008 graduate of the University of Southern Maine who now lives in Rockland, was the fastest Mainer on

Monday. He placed 32nd among men with a time of 2:33:30.

With one marathon under his belt, a 2:24 performance in Philadelphia in November, Wheeler throttled back his Boston expectations and actually enjoyed himself.

“It was better than I thought it was going to be,” he said. “Considering how I usually do in these conditions, it was pretty good. I’m happy with it.”

Wheeler works for an energy efficiency company in Rockland, caulking cracks and installing insulation. He’s been to Boston before for workouts but had never experienced the sensation of running through streets lined with spectators.

“It was great,” he said. “The crowd was awesome.”

He particularly enjoyed those spectators who provided garden hoses to shower runners along the course and gulped water or sports drinks at every aid station.

“I took a ton of water,” he said. “I made sure I kept myself cool, because I knew that would be the key.”