At age twenty-four, Miller (a Republican) was elected mayor of Goshen. He held no other political offices until his election as Indiana Attorney General.[2]
Miller was elected Attorney General in 1902, succeeding William L. Taylor. He served as Attorney General in the administration of Republican GovernorsWinfield T. Durbin and Frank Hanly. In 1906, Miller (breaking with former Attorney General Alonzo G. Smith's decision on the matter) supported the state government's lawsuits against hotel companies in French Lick and West Baden Springs regarding illegal gambling. Also, in 1906, Miller reviewed and approved the appointment of Mary Stubbs to the office of state statistician. Mary Stubbs had previously served as assistant to the former statistician, her father, Joseph Stubbs, but he had died while in office. Governor Hanly nominated Mary Stubbs to her father's former position. Despite the controversy surrounding the appointment due to Stubbs's gender, Miller declared that Governor Hanly had the authority to nominate a woman for the position. Additionally, Miller earned the ire of labor organizations in East Chicago due to his opposition to a bill regarding Calumet Rivercanal construction. The Brotherhood of Railroad Trainmen declared Miller an enemy of labor unions and opposed his re-election campaign. Despite this, Miller was re-elected to the position in 1904. He served until 1907, when he was succeeded by James Bingham.[2][5][6]
Miller was president of the State Bank of Goshen, the Elkhart County Loan and Trust Company, and two local telephone companies. He also served as secretary of Lesh, Prouty & Abbott Company, a walnut lumber manufacturing business in East Chicago.[4]