At 100, Sisters Will Celebrate With a Party : Longevity: They are the oldest identical twins in the U.S., says the Guinness Book of World Records.

Marian Lamb Bechtelheimer of Thousand Oaks doesn’t take any pills, hasn’t seen a doctor in three years and will celebrate her 100th birthday today with her identical twin sister, Mary Elizabeth Lamb Sheridan.

How did she live to be so old?

“I don’t know,” she said Friday at the Thousand Oaks Residential Care Home.

Then she quarreled with the very premise of the question.

“I don’t think I am old,” she said. “I think I’m young.”

While Bechtelheimer may be young in her mind, she and her sister are indeed old. In fact, according to the Guinness Book of World Records, they are the oldest identical twins in the United States.

Born in Santa Barbara in 1895, the twins moved to Ventura and graduated in 1914 from Ventura High School, where they were star tennis players.

In high school, the two looked so alike that they sometimes traded dates. The boys never suspected a thing, Bechtelheimer said with a laugh.

She moved to the San Fernando Valley in 1917 with her first husband. The couple grew walnuts and apricots on an 80-acre farm in what is now Canoga Park. He died in 1937. Her second husband, also deceased, was a pharmacist.

While Bechtelheimer moved back to this area only six years ago, her sister returned to Santa Barbara after high school and has lived there ever since. Sheridan also was married, and her husband too is deceased. She lives at the Olive Gardens Residential Care Home.

Although Bechtelheimer did not offer any insights into the secret of her longevity, her friends and family quickly gave their opinions on how the twins joined that select club of centenarians.

“I think they have lived so long because they are so active,” said Peggy Eggleston, 74, Bechtelheimer’s daughter. She said that in addition to tennis, the two were swimmers and loved to walk on the beach.

“She never smoked, and she never was a drinker,” said Carol Bealer of Moorpark, a granddaughter of Bechtelheimer.

“I think it’s genetic,” said Alida Hartley, the receptionist at the Thousand Oaks home.

The twins had five children, 18 grandchildren and 34 great-grandchildren.

Their birthday party today will be at the same Santa Barbara church where the two were baptized. It will be their first reunion since their 97th birthday party.

“That’ll be dandy,” Bechtelheimer said.

Not that she is dissatisfied with her day-to-day existence.

“I just live here. This is my home. I like it here,” she said. “I don’t worry. I’m a very happy person.”

Part of her disposition, she and her family admit, may stem from a memory that is selective and sometimes faulty.

“I’ve forgotten a lot of things,’ Bechtelheimer said.

Hartley said Bechtelheimer, her purse slung over her walker, spends most of her day “directing traffic” in the rest home’s lobby.

Indeed, she loudly chastises those who enter through the front door.

“Shut the door; it’s cold,” she told one visitor Friday.

Hartley said some visitors are taken aback by the scolding, but forgive her as soon as they find out Bechtelheimer’s age.

Indeed, the age is impressive even to the chewing gum folks at the Wrigley Co., no stranger to the subject of twins.

“Wow,” said Bill Piet, a spokesman for the Chicago company. “We certainly wish them well.”