HOPKINTON, Mass. (AP) — Workers zip in and out of the tents that dot the Hopkinton Town Common, flags flutter from the gazebo, and crews assemble the platform where the starter will fire the gun to send the Boston Marathon field on its way. On race day, this otherwise sleepy New England town serendipitously located 26.2 miles from Boston will swell to three times its size.

Once a year for the last 100 years, Hopkinton becomes the center of the running world, thanks to a quirk of geography and history that made it the starting line for the world’s oldest and most prestigious annual marathon.

“It wouldn’t be the Boston Marathon without Hopkinton,” said Meb Keflezighi, who was conferred with honorary town citizenship after winning the race in 2014, the year after the finish line bombing. “As the sign says, ‘It all starts here.’”

Although the Boston Marathon was born next door in Ashland, where 15 men toed a line near Metcalf’s Mill in 1897, the start was moved to Hopkinton in 1924 to conform with a new international distance standard. With a field for the 100th anniversary that will top 30,000 runners, the town strains to absorb the crowds and yet still maintains its small-town hospitality year-round.