“The ball is in Congress’s court,” said Justice Ruth Bader Ginsburg two years ago, taking the unusual step of announcing a passionate dissent from the bench as the Supreme Court ruled against Lilly Ledbetter, May 29, 2007.

Today, Lilly Ledbetter watched President Obama sign a law that reverses that ruling. But who is she?

For nearly 20 years, from 1979 until she retired in 1998, she worked as a supervisor at Goodyear’s tire plant in Gadsden, Ala. She was an area manager, one of the few women in such a position. At first, her pay was in line with what the men in the same job made. Then it slipped. By the end of 1997, she made $3,727 a month. The lowest paid man doing that same work made $4,286 a month, and the highest paid men were getting $5,236. So she sued.

“I just could not believe that they would separate the female pay so far down the line from my male peers,” she told NBC News at the time. “I was shocked when my attorneys accumulated all the information, and I saw how low it was.”

Her legal argument was this: Every time the company wrote her a check, it was committing sex discrimination. But she lost. The Supreme Court, by a 5-4 vote, said she waited too long to sue. The majority said federal law requires workers to file their complaints within 180 days of an act of discrimination. In other words, the court said, that clock starts ticking when an employer decides how much to pay, not each time a paycheck is written, years later.