Mary began writing seriously after the stock market crash of 1903. She was 27 that year, and wrote 45 short stories. Her first mystery novel was published in 1906. “The Circular Staircase”, published in 1907, was the novel that propelled her to national fame. According to Mary's obituary in the “Pittsburgh Post-Gazette” in 1958, the book sold 1.25 million copies. In 1911, after the publication of five successful books and two plays, the Rinehart family moved to Glen Osborne, Pennsylvania. Today there is a Mary Roberts Rinehart Nature Park in the borough of Glen Osborne at 1414 Beaver Street, Sewickley, Pennsylvania.
During the First World War, Mary worked as a war correspondent for “The Saturday Evening Post” on the Western Front, during which time she interviewed KingAlbert I of Belgium, Winston Churchill and Mary of Teck, the wife of King George V. Of that encounter Mary Rinehart wrote: "This afternoon I am to be presented to the queen of England. I am to curtsey and to say 'Your majesty,' the first time!" She reported on developments to the American War Department and was in Paris when the First World War Peace Treaty was signed.
Mary contributed regularly to “The Saturday Evening Post” and was a prolific writer. During her prime, she was reputed to be even more famous than Agatha Christie. When Mary died on 22nd September 1958, her books had sold over 10 million copies.
