Former South Dakota Gov. Walter D. Miller in 2012 outside the State Capitol in Pierre, S.D. (Lance Nixon/ PIERRE CAPITAL JOURNAL VIA ASSOCIATED PRESS )

Former South Dakota governor Walter D. Miller, who stepped in as the state’s leader in 1993 after a plane crash killed his predecessor, died Sept. 28, it was reported from Sioux Falls. He was 89.

The office of South Dakota Gov. Dennis Daugaard (R) announced the death but did not provide a cause.

Mr. Miller served as the state’s 29th governor through 1995, taking the oath of office on April 20, 1993, a day after the plane carrying Gov. George Mickelson (R) and seven others went down in eastern Iowa.

The tall, lanky cowboy epitomized the western South Dakota rancher, and Mr. Miller almost never appeared in public without his cowboy boots. A toothpick often dangled from his mouth, and when he ventured outside, he completed the look with a cowboy had and a western-style sport coat.

Mr. Miller was a prominent Republican member of the state House of Representatives from 1967 through 1986, and he was the only person in state history to serve as speaker, speaker pro tempore, majority leader, assistant majority leader and majority whip.

When George Mickelson won the 1986 gubernatorial race, he made Mr. Miller the state’s first full-time lieutenant governor and appointed him chairman of a number of task forces. At the time, Mr. Miller said he had no political ambitions and wanted only to help make the Mickelson administration a success.

But all that changed six years later, when Mickelson died in the plane crash. Within months, Mr. Miller decided to seek his own term as governor in the 1994 election but lost in the GOP primary to Bill Janklow, who went on to win another term as governor after previously serving eight years in that role.

Walter Dale Miller was born near the South Dakota towns of Viewfield and New Underwood on Oct. 5, 1925, and spent his life on his family’s ranch.

After attending the South Dakota School of Mines and Technology, he ran the 7,000-acre family ranch and was president of the Dakota National Life Insurance Co. from 1970 to 1985.

Mr. Miller and his first wife, Mary Randall, who died in 1989, had three daughters and one son. In 1993, Mr. Miller married Pat Caldwell, who had been his executive assistant in the lieutenant governor’s office.

— Associated Press