The tight writing schedules and frequent travel eventually impacted Tarbell's health. On the verge of physical collapse, she checked into the Clifton Springs Sanitarium near Rochester, New York in 1896. Besides rest and relaxation, her treatment included taking the water cure. She would visit the Sanitarium numerous times over the next thirty years. Tarbell continued to write profiles for McClure in the late 1890s. While there, she had the opportunity to observe the United States expansion into imperialism through the Spanish–American War. She was writing a series on military affairs, and in 1898 she was set to interview Nelson A. Miles, the commanding general of the United States, when the battleship the USS "Maine" was blown up in Havana Harbor. Tarbell was allowed to keep her appointment nonetheless and observe the response at the U.S. Army Headquarters. Theodore Roosevelt was already organizing what would become the Rough Riders, and Tarbell said that he kept bursting into the Army office, "like a boy on roller skates." Tarbell longed for her old life in Paris, but realized she was needed in America: "Between Lincoln and the Spanish–American War [as it became known] I realized I was taking on a citizenship I had practically resigned". Tarbell moved to New York and accepted a position as Desk Editor for "McClure's" in 1899. She was paid $5,000 a year and given shares in the company, which made her a part-owner. She rented an apartment in Greenwich Village which reminded her of France. She frequented the Hotel Brevoort, where Samuel Clemens (Mark Twain) also dined. Her position as editor was to fill in for Samuel McClure, as he was planning to be away from the office for several months. Tarbell was to become known as an anchor in the office while the magazine built out its roster of investigative editors and authors. She and Phillips were described as the "control" to S. S. McClure's "motor." "McClure's" sent Stephen Crane to cover Cuba during the War. Ray Stannard Baker was hired by the magazine to report on the Pullman Strike. Fiction editor Violo Roseboro discovered writers such as O. Henry, Jack London, and Willa Cather. John Huston Finley quit his job as president of Knox College and became an editor for "McClure's". In 1902, she began publishing serialized articles in "McClure's" that were later collected in the book, "The History of the Standard Oil Company" (1904).