GROTON -- Five generations from at least as many states -- from Virginia to Florida to California -- gathered at the Groton Senior Center on Sunday to mark perhaps one of the rarest occasions in the United States: the 100th birthday of twins.

Ruth Wilson and Eva Morin (nee Clark) were born on a Carlisle farm in 1914 at the start of World War I. The sisters are the third-oldest pair of twins in the country still alive to celebrate a birthday in the new century.

"I can't say how they were able to live so long," said Eva's daughter, Suzanne Morin of her mother and aunt's longevity. "Ruth smoked for a while, but Eva did not."

Both Ruth, a practicing nurse until she was 65, and Eva, who moved about with her minister husband, lived different lives, so on the surface, they did not seem to have done much in common.

"I think it was because they both grew up on a farm, with all that fresh air," guessed Martha Nevala, Ruth's daughter.

The sisters, however, have their own theories.

"I never smoked and I never drank," Eva said. "I ate good food and spent my time doing good deeds."

"We spent a lot of time outdoors and running in the fields," Ruth added. "But I believe a lot depends on your genes. The members of our family have always been very healthy."

Younger brother Edward Clark, 88, chalked up his sisters' longevity to their personalities.

"They were both strong-willed," Clark said.

Ruth and Eva were born May 19, 1914, the year Henry Ford installed the first automobile assembly line and Franz Ferdinand, archduke of Austria, was assassinated, igniting World War I. Since then, the sisters have witnessed the entire panoply of the 20th century as the world progressed from horsepower to high-speed Internet.

"I've seen many wonderful things over the years," Eva said. "I remember that when a plane flew overhead, we'd all run outside to see it. But I worry about the United States and about the children of today."

"I think it's terrific," said Ruth's granddaughter, Sandy McCarthy. "I never would have imagined that this could happen and am glad that both sisters are as healthy as they are."

McCarthy had done some research on the Internet and discovered that Ruth and Eva are the third-oldest set of twins in the United States and possible candidates for the "Guinness Book of World Records."

"I count myself lucky to have her," said Ruth's great-great-granddaughter, Jessica McCarthy. "She is just amazing. She helped take care of me when I was growing up, and her being in nursing made me want to go into nursing, too. She's been an inspiration to me."

"It's just fantastic that they are both in such good spirits," said niece Jacky Goodie, who traveled from Virginia for the party. "Ruth was always very outgoing, very sociable. She was the adventurous one. She even went kayaking on her 90th birthday."

"Eva was the quieter one," agreed fellow niece and Tyngsboro resident Dotty Marinel. "Ruth always thought she'd never get older. She always thought of herself as a teenager or a glamour girl."

That's an attitude hinted at in some of the many contemporary photographs of the twins over the years, shown in a PowerPoint presentation on the Senior Center's overhead flat-screen TV -- something only dreamed about in 1914, when even forward-thinking science fiction was in its infancy.

"Eva was a little more down-to-earth," Marinel said. "She was a good cook who would always have to invite you for tea. She painted, too, working in watercolors."

For the last 25 years, Ruth has lived at Groton Commons. She married Frank Wilson, while sister Eva currently lives in Chelmsford, where she lived with her husband, Roland Morin, who had once served there as minister of that town's Unitarian Church.

Raised on a farm, the twins had a number of siblings including Katherine and Romey, in addition to Edward.

Ruminating over the people they have known and the events they have witnessed since 1914, Ruth thought there was more to the question of her and her sister's long lives than simply the inheritance of good health. She continues to look forward to the future.

"I believe that God has a plan for everybody," Ruth said. "There's a verse in the Bible that I like. It's from Timothy and goes like this: 'For God hath not given us the spirit of fear; but of power, and of love, and of a sound mind.'

"I think His plan for my life is to live. I feel there is still something that I have to do before I die."