More than a century ago, America’s longest practicing doctor and the 56th oldest person in the world was born in Portal, Ga. Sunday, she will celebrate her 111th birthday.

Dr. Leila Denmark, who now resides in Athens with her daughter, helped develop a vaccine for the whooping cough and was a practicing pediatrician for 73 years. Even after she retired due to failing eyesight, patients still called to ask her advice.

She is no longer in good enough health to do interviews, but her daughter, Mary Hutcherson, was able to discuss Denmark’s life.

Hutcherson said her mother did not plan on being a pediatrician, but her fiancé, John Eustace Denmark, was sent to Java, Indonesia, with the State Department, and the couple decided to postpone their marriage. Denmark enrolled in

medical school, although it was unusual for a woman to be a doctor in the 1920s.

“Mother was small but determined,” Hutcherson said. “She applied, but they turned her down.” But Denmark wouldn’t accept “no” for an answer and was admitted as the only woman in her class for what she has always described to her daughter

as “four wonderful years” at the Medical College of Georgia.

“All her life she’s wanted to help people,” Hutcherson said. Denmark worked with children at Grady Hospital in Atlanta, and admitted the first patient as a resident at Children’s Healthcare of Atlanta at Egleston.

In the 1930s, she began research on the whooping cough and with the help of researchers from Emory University, developed the vaccine that is still used today.

“She was always research-oriented,” Hutcherson said. “She wanted to find out how things worked.”

After an internship at Philadelphia Hospital, she began a private practice in pediatrics in 1931. She saw patients in her home in Alpharetta until 2001, often caring for several generations of the same family.

Denmark “worked with preventative medicine rather than trying to patch up,” Hutcherson said. “She believed that the greatest thing that ever happened for children was baby food and immunization.” Denmark had no patience for those who refused to have their children vaccinated. But when problems arose, she was able to solve them.

“I have always thought that Mother was a fantastic diagnostician,” Hutcherson said. “She could come to the conclusion right away and was almost always right.”

Denmark is known to this day for her beliefs on childcare and parenting. In 1971, she published a book titled “Every Child Should Have a Chance.”

Madia Bowman, a mother of 11 who took all her children to Denmark, later published another book, “Dr. Denmark Said It!,” filled with advice and interviews with Dr. Denmark.

“She is well known for her emphasis on scheduling,” Bowman said. “She believes that from infancy, every child should be on a good schedule of eating and sleeping. She has a real emphasis on good nutrition, and she believes that [it] is equally, if not more, important than medication.”

Denmark was one of the first doctors to advise against alcohol, drugs, caffeine and smoking while pregnant. Hutcherson said that she always recommended that babies sleep on their stomachs, regardless of the conflicting advice over the years on that subject.

Denmark’s choice to practice out of her home illustrates another of her parenting beliefs. Bowman said that Denmark made no house calls and did not attend medical conventions so that she could be at home with her daughter.

“She had a real focus on mothers staying home,” Bowman said. “She believes that children need to stay at home with their mothers rather than being put in day care,” Bowman said. “One of the most wonderful things about going to her was that you came out encouraged and inspired that your job was central to society and that no one could fill your place as a mother.”

For people of all ages, Bowman said that Denmark’s advice was to “eat right, take care of yourself, behave yourself and be happy. [Denmark] said, ‘I never worked a day in my life.’ She loved what she did.”

“Never do anything you’re going to be sorry about later down the line,” Hutcherson said, quoting her mother’s advice. In book signings, Denmark often wrote, “Do what you can to help.”

Hutcherson attributes her mother’s long life partly to a healthy diet that includes lean roast beef, vegetables and very few sweets.

“She came from a family with lots of heart disease and managed to escape that.” And, she said, “the fact that she stayed busy so long and was interested in things. She kept looking forward; she never looked back.”