Born at New York; studied at the Free Academy or College of the City of New York, and in 1859 received the MD of the New York College of Physicians and Surgeons. During the North and South War he served as Assistant Surgeon to the Federal Army and was from 1862 in charge of the General Hospital at Frederick, Maryland. At the Peace he settled in practice in New York and for many years was Attending Surgeon at the New York, Roosevelt, St Luke's, and St Vincent's Hospitals. He was also for years, together with William T Bull, Professor of Surgery at Columbia University, joining the Faculty in 1873, becoming Professor in 1884, and retiring in 1900. He commenced surgery under older conditions, but adopting Lister's methods early he rapidly developed a reputation in the surgery of bones, joints, and intestinal surgery, particularly in relation to appendicitis, duodenal ulcers, and gastro-enterostomy. He was President of the New York Academy of Medicine in 1901-1902. In 1900 he was President of the American Surgical Association and received the Hon FRCS. When the American College of Surgeons was organized in 1913 Weir was one of the five surgeons created Hon Fellows. He died in his ninetieth year at the home of his daughter in New York, on April 6th, 1927. There is a portrait of him in the Hon Fellows' Album. Another accompanies the obituary in the *American Journal of Surgery* (1927, NS ii, 514), the original of which, by John A Weir, representing him in the FRCS gown, is in the New York Academy of Medicine. Publications: Weir's very numerous publications commence with *Photographs of Surgical Specimens from the United States General Hospital, Frederick, Maryland*, 4to, 49 plates, np, nd.