The book was published by George M. Hill Company. Its first edition had a printing of 10,000 copies and was sold in advance of the publication date of September 1, 1900. On May 17, 1900, the first copy of the book came off the press; Baum assembled it by hand and presented it to his sister, Mary Louise Baum Brewster. The public saw the book for the first time at a book fair at the Palmer House in Chicago, July 5–20. The book's copyright was registered on August 1; full distribution followed in September. By October 1900, the first edition had already sold out and the second edition of 15,000 copies was nearly depleted.
In a letter to his brother Harry, Baum wrote that the book's publisher, George M. Hill, predicted a sale of about 250,000 copies. In spite of this favorable conjecture, Hill did not initially predict the book would be phenomenally successful. He agreed to publish the book only when the manager of the Chicago Grand Opera House, Fred R. Hamlin, committed to making The Wizard of Oz into a musical stage play to publicize the novel. The play The Wizard of Oz debuted on June 16, 1902. It was revised to suit adult preferences and was crafted as a "musical extravaganza". The music was written by Paul Tietjens and the costumes were modeled after Denslow's drawings. Anna Laughlin starred as Dorothy, David C. Montgomery was the Tin Woodman, and Fred Stone was the Scarecrow. Montgomery and Stone immediately became stars, with the Chicago Tribune 's printing pictures of the two in their costumes and stating, "To Montgomery and Stone, The Tribune awards the honors of pioneers in original comedy." After Hill's publishing company became bankrupt in 1901, Baum and Denslow agreed to have the Indianapolis-based Bobbs-Merrill Company resume publishing the novel.
Baum's son Harry Neal told the Chicago Tribune in 1944 that L. Frank told his children "whimsical stories before they became material for his books". Harry called his father the "swellest man I knew", a man who was able to give a decent reason as to why black birds cooked in a pie could afterwards get out and sing.
By 1938, over one million copies of the book had been printed. Less than two decades later, in 1956, the sales of his novel had grown to 3 million copies in print.