Robert O'Reilly was born on January 14, 1845, in Philadelphia, Pennsylvania. He was descended from an old Irish family, one branch of which, emigrating to Spain, produced Gen. Alexander O'Reilly, who was captain general of Cuba and one of the Spanish governors of Louisiana. The American branch settled in Pennsylvania before the Revolution and it was in Philadelphia that, to John and Ellen (Maitland) O'Reilly, Robert was born.
Robert O'Reilly was educated in the public schools of his native city, Philadelphia, and had begun the study of medicine when the Civil War commenced. With the close of the Civil War he resumed his medical studies at the University of Pennsylvania and was graduated in 1866.
When the Civil War began, Robert O'Reilly was appointed an acting medical cadet and assigned to the Cuyler General Hospital in Philadelphia; later he served as a medical cadet in a hospital at Chattanooga and in the office of the medical director of the Army of the Cumberland. In May 1867 he was appointed assistant surgeon in the army and was sent out to California by way of Panama with a detachment of recruits. From 1868 to 1869 he was in Arizona with troops operating against hostile Indians. In 1874 he participated in the Sioux campaign in Wyoming and Montana. While on duty incident to labor disturbances in Pennsylvania in 1877, he sustained an injury which incapacitated him for two years.
Soon after his return from sick leave, he was assigned to duty as attending surgeon in Washington. In this capacity his attractive personality and his professional skill made him a prominent figure in the capital. He was the White House physician during the two administrations of President Cleveland, with whom he was on terms of intimate friendship. Following the outbreak of the Spanish-American War, O'Reilly, then a major, was chief surgeon of Gen. John J. Coppinger's division at Mobile, Alabama, and later was transferred to the staff of Gen. J. F. Wade in Havana. The medical department ship Bay State was placed at his disposal and he was sent to Jamaica for the purpose of acquiring information relative to the experience of the British army in tropical hygiene. He made a study of the housing, food, and care of troops, and submitted recommendations in relation to these subjects which were of material value.
Returning from Cuba in November 1899, he commanded the Josiah Simpson Hospital at Fort Monroe, Virginia, and later was transferred to San Francisco as chief surgeon of the department of California. On September 7, 1902, he succeeded William H. Forwood as surgeon-general of the army. General O'Reilly brought into his office a group of highly intelligent young officers and organized it into divisions, each with a responsible head.
Unsatisfactory conditions in the army disclosed by the Spanish War caused the appointment of the Dodge Commission by President McKinley. The findings of the commission relating to the medical department took the form of a number of recommendations, which it devolved upon General O'Reilly to carry out. Among other reforms which resulted was a reorganization of the medical corps and the creation of the medical reserve corps. Robert O'Reilly was president of the board which recommended the adoption of typhoid prophylaxis for the army.
In 1906 he represented the United States at the international conference at Geneva, Switzerland, for the revision of the Geneva Convention.
O'Reilly was retired for age on September 14, 1909, and continued his residence in Washington until his death three years later from uremic poisoning.
O'Reilly's notable accomplishments include: a position as the physician at the White House during both of President Grover Cleveland’s administrations; Chief Surgeon of the First Independent Division at the beginning of the Spanish-American War; delegate at the International Conference for the Revision of the Geneva Convention in Geneva in 1906; the 20th Surgeon General of the United States Army. Robert O'Reilly was co-author of the American Textbook of Surgery (1903).
O'Reilly was a man who won affection and loyalty from all who came into intimate contact with him. Though of a sensitive and retiring disposition he had an unfailing fund of courtesy and good nature.
On August 16, 1877, Robert O'Reilly married Frances L. Pardee of Oswego, New York. They had two children.
