Daly was born in Western Pennsylvania and spent most of his professional life as a leading medical practitioner in Pittsburgh. He served on both sides in the Civil War, hunted with Buffalo Bill and General Nelson A. Miles, and traveled extensively, studying at leading hospitals in Europe. His fame rested initially on his pioneering work in the specialties of laryngology and rhinology. Later in his career, however, it was the imbroglio he caused as major and surgeon-in-chief of the U.S. Volunteers during the Spanish-American War that brought him national notoriety. In 1898, Daly became enmeshed in a controversy popularly referred to as the "embalmed beef scandal." Having found the purveyors of beef to the Army were experimentally using hazardous preservatives on the meat, Daly convinced his friend, General Miles, to take on the War Department. The ensuing trial attracted national attention and resulted in the forced resignation of Secretary of War Russell A. Alger and the court-martial of Commissary General Charles P. Eagan. Daly's role in bringing attention to the activities of the meatpacking industry cannot be overstated. The sensational outcome of the hearings remained in the news for months and caught the public eye. It was not long before Upton Sinclair and others began their clarion calls for government intervention that resulted in passage of the Pure Food and Drugs Act and the Meat Inspection Act in June 1906.