Heritage Auctions had estimated that they would fetch $US3 million ($A4.7 million) or more.
Online bidding opened last month and by Friday had reached $US1.55 million ($A2.43 million), said Robert Wilonsky, a vice president with the Dallas-based auction house.
More than 800 people were tracking the slipper, and the company's web page for the auction had hit nearly 43,000 page views by Thursday, he said.
As Rhys Thomas, author of the book, The Ruby Slippers of Oz, puts it, the sequined shoes from the beloved 1939 musical have seen "more twists and turns than the Yellow Brick Road".
They were on display at the Judy Garland Museum in her hometown of Grand Rapids, Minnesota, in 2005 when Terry Jon Martin used a hammer to smash the glass of the museum's door and display case.
More than 800 people were tracking the slippers before the auction. (AP PHOTO)
Their whereabouts remained a mystery until the FBI recovered them in 2018.
Martin, now 77, who lives near Grand Rapids in northern Minnesota, wasn't publicly exposed as the thief until he was indicted in May 2023.
He pleaded guilty in October 2023. He was in a wheelchair and on supplementary oxygen when he was sentenced in January to time served because of his poor health.
His lawyer, Dane DeKrey, explained ahead of sentencing that Martin, who had a long history of burglary and receiving stolen property, was attempting to pull off "one last score" after an old associate with connections to the mob told him the shoes had to be adorned with real jewels to justify their $US1 million ($A1.6 million) insured value.
The shoes were returned in February to memorabilia collector Michael Shaw, who had loaned them to the museum.
They were one of several pairs that Garland wore during the filming, but only four pairs are known to have survived. In the movie, to return from Oz to Kansas, Dorothy had to click her heels three times and repeat, "There's no place like home".
Among those bidding was the Judy Garland Museum. The city of Grand Rapids raised money for the slippers at its annual Judy Garland festival to supplement the $US100,000 ($A156,470) set aside this year by Minnesota lawmakers to help the museum buy the slippers.
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