PLYMOUTH, Mich.

WHEN Margaret Dunning was 10 years old, she lost control while driving the family’s Overland touring car and careered into a barn, fracturing several boards.

“I hit it, and it didn’t move,” Ms. Dunning, who turned 101 last month, said.

“That car had a mind of its own,” she said. “And I’m not a very tall person, so I had trouble getting onto the brakes with enough power to hold that engine down. It just got away from me.”

Soon enough, though, she was back at it, rumbling around the back roads of Redford Township, just west of Detroit, where her family owned a sprawling dairy and potato farm. By then she had already been driving for two years.

Before the barn incident, Ms. Dunning’s father had often let his young daughter steer while he operated the other controls. One day he let her do it all, but not without a stern lecture.