Bob Ortega, author of "In Sam We Trust," a history of Wal-Mart, said Clinton used her position to urge the company to improve its gender and racial diversity. Because of Clinton's prodding, Walton agreed to hire an outside firm to track the company's progress in hiring women and minorities, Ortega said.

"These were things the company was not addressing and wouldn't have, had she not pushed them to do so," Ortega said. "She's somebody who could definitely get things done."

In fact, Clinton proved to be such a thorn in Walton's side that at Wal-Mart's annual meeting in 1987, when shareholders challenged Walton on the company's lack of female managers, he assured them the record was improving "now that we have a strong willed young lady on the board."

Clinton was particularly vocal on environmental matters, pressing the company to boost its sale and use of recycled materials and other "green" products.

Garry Mauro, who served with Clinton on a Wal-Mart environmental advisory committee, pointed to many successes, such as persuading the company to establish recycling centers and sell products like recycled oil and long-life light bulbs.