Lt. Gov. Win Rockefeller, the unassuming billionaire who last year abandoned a race for Arkansas governor — a post once held by his father — died Sunday after unsuccessful treatments for a blood disorder, his office said. He was 57.

Rockefeller died Sunday morning at the University of Arkansas for Medical Sciences with his family present, said Steve Brawner, the lieutenant governor's spokesman. Rockefeller had returned to Arkansas on July 8 after two unsuccessful bone marrow transplants to treat a blood condition that can lead to leukemia.

Rockefeller had undergone transplants Oct. 7 and March 29 in attempts to cure an unclassified myeloproliferative disorder. The lieutenant governor notified Gov. Mike Huckabee immediately on his return to the state that he could not continue in his duties, at least temporarily.

The great-grandson of Standard Oil founder John D. Rockefeller ranked No. 283 on the Forbes magazine list of the nation's wealthiest people in 2005, with a fortune the magazine estimated at $1.2 billion. As lieutenant governor, a part-time job, he forwarded his $34,673 state salary to charity.

He was the son of former Gov. Winthrop Rockefeller, who was elected to two-year terms in 1966 and 1968. His father died in 1973 at age 60 of cancer.

The lieutenant governor, a Republican, entered politics in 1996. He won a special election for lieutenant governor to complete the unexpired term of Huckabee, who became governor July 15, 1996, after Jim Guy Tucker was convicted as part of the Whitewater investigation. Rockefeller won re-election twice, in 1998 and 2002.

Under the state's term-limits law, he could not serve again as lieutenant governor. He announced his candidacy for governor last year but withdrew July 19, 2005, after the blood disorder was diagnosed.

Before withdrawing, he had said he wouldn't rely on his fortune to purchase the office.

"I don't think the governor's office is there to be bought by anybody. Nobody is ordained or destined to be governor. A person has to earn the right to serve," he said in February 2005.

As lieutenant governor, he served as an economic cheerleader for the state, traveling at his own expense to seek foreign investments here.

After his father's death, Rockefeller bought Winrock Farms Inc. and became involved in banking, retailing, automobile dealerships and resorts. Long before holding an elective office, Rockefeller was active in public service.

He was a member of the Arkansas State Police Commission from 1981 to 1995 and was chairman of the President's Council on Rural America after his appointment to the council in 1991 by the first President Bush.

Rockefeller supported literacy councils and in 1997 created the Books in the Attic program, in which Boy Scouts collect used books to distribute to families. With two children with Down syndrome, Rockefeller and his second wife, Lisenne, started what is now the Academy at Riverdale, a school for children with learning disabilities.

Rockefeller also founded The Billfish Foundation, an organization dedicated to protecting marlins, swordfish and other billfish. As a National Rifle Association member, he sponsored Project ChildSafe to distribute free trigger locks in the state.

He also served on the Boy Scouts' national board of directors and was president of the Scouts' local Quapaw Area Council. He was on the national boards of Ducks Unlimited and The Nature Conservancy, and on the boards of the Arkansas Cancer Research Center and the Arkansas Arts Center Foundation.

Born Sept. 17, 1948, in New York, Rockefeller was the only child of Winthrop Rockefeller and Barbara "Bobo" Sears, the daughter of an immigrant Lithuanian coal miner. An uncle was former vice president Nelson Rockefeller, and current U.S. Sen. Jay Rockefeller, D-W.Va., is a cousin.

Rockefeller attended Pembroke College at the University of Oxford and graduated from the ranch management program at Texas Christian University. Rockefeller had homes at Winrock Farms in Conway County and in Little Rock. He had eight children.

Rockefeller's father was Arkansas' first Republican governor since Reconstruction, after moving to the state in 1953. He headed the Arkansas Industrial Development Commission in the 1950s and 1960s and is credited with attracting more than 600 businesses and 10,000 jobs to the state.

While the elder Rockefeller was governor, Arkansas passed minimum wage and freedom of information laws, and his tenure is generally regarded as a watershed moment for the state as it broadened its agriculture-based economy and made efforts to improve schools and race relations.