Marlo Thomas, Spokesperson for St. Jude's Children's Hospital

In 1991, after her father died, actress Marlo Thomas planned to carry on his work at St. Jude Children's Research Hospital just long enough to see the facility through a period of transition. But it didn't take long for Thomas to feel the same calling that had inspired her father, entertainer Danny Thomas, to establish the Memphis-based pediatric hospital in 1962, with the dream that "no child shall die in the dawn of life."

"I was pulled in by the mothers and fathers waiting to find a miracle cure," says Thomas, with the same wide-eyed expression that made her America's sweetheart in the 1960s sitcom That Girl.

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Today, Thomas works tirelessly as national outreach director for St. Jude—making guest appearances, hosting fundraising events (with her husband of 26 years, Phil Donahue), and using her celebrity to raise money and awareness to support cutting-edge research and treatment of pediatric cancers and other diseases. This year alone, researchers at St. Jude—which never charges families more than their insurance will cover—have developed new treatments for childhood brain cancer, made advances in understanding the hearing loss that affects children who undergo chemotherapy, and pioneered the production of a vaccine that could stave off avian flu.

Thomas's ultimate goal? "To close our doors someday," she says, flashing a That Girl smile. This girl means business. Her father would be proud.

*The name of this award was originally the Impact Award. In 2008, the awards were renamed as the Inspire Awards.