Many of America’s most successful entrepreneurs and business executives started out at the bottom of the career ladder. Some of them began their careers at the same company which they now lead, working long hours and hatching new business ideas en route to a management position.

In our regular First Job Friday feature on Information Station, we profile these success stories and their experiences in corporate America. This week, we’re highlighting Mary Barra, the first female CEO of General Motors (GM). Barra has spent more than three decades at the company, starting when she was an 18-year-old in search of quality work experience to bolster her academic credentials. In Barra’s words:

“My first job at General Motors was as a quality inspector on the assembly line. I had a little scale and clipboard. At one point, I was probably examining 60 jobs an hour during an eight hour shift.”

As a quality inspector, she was forced to meet rigorous deadlines and high quality standards to deliver the best possible product to drivers.

And what did Barra learn? “A job like that teaches you to value all the people who do a job like that,” she explains. That know-how has helped the GM lifer understand her employees and harness their potential for the betterment of the company. And it’s made her successful on all rungs of the career ladder—from the assembly line to the C-suite.