“Who wants to read about this old lady?” she said. “I’m asked all the time about the secret to my longevity. It’s a balanced life, I tell them. The way I look at it, age is just a number. It’s what you do with your time that really counts. When you look back over what happened in your life, you see the things that made you what you are. In my case, those things made me a very determined person.”

For 43 million Americans and almost 800 million people worldwide who still struggle to fill out a job application or read a bedtime story to their children, Ruth Johnson Colvin is hardly a household name, and for most of them written accounts of her life are still beyond reach. She was born Ruth Johnson in Chicago on Dec. 16, 1916, the oldest of five children of Harry and Lillian Johnson, who shared the same Swedish surname.

Ruth and her siblings, Harriette, Harry Jr., George and Lucille, were raised in Chicago. Her father, a businessman who was an owner of a construction company, died when Ruth was 12. Her father had set aside money for college for all his children. But when Ruth graduated from Fenger Academy High School in Chicago in 1934, she learned that an uncle, the executor of her father’s estate, had reserved the college money for her brothers, and would pay her expenses only for a secretarial school, because she was “just a girl,” as she put it.

Undaunted, an avid reader with excellent grades, she attended night classes at Thornton Junior College in Harvey, Ill., graduating after two years with an associate degree in 1936.

“But that was a blessing in disguise,” she said, “because it was there, in those night classes, that I met the future love of my life, Robert John Colvin, who was to be my life’s partner for 73 years. We barely knew one another at that time, though. We were each dating someone else.”