Joseph O'Neil was born in
Brooklyn, New York, on December 27, 1863, the son of Mary Ann Burke and Major Joseph O'Neil, a
Union Army veteran of the
American Civil War. After his father's 1867 death, O'Neil's mother married army officer John Murphy, and O'Neil was raised at Army posts throughout the United States. He graduated from the
University of Notre Dame in 1883. In 1884, O'Neil joined the army as a
second lieutenant and was assigned to the
14th Infantry Regiment, the same regiment in which his stepfather was then serving, which was then stationed at
Vancouver Barracks. From there, he explored the region around
Mount Olympus in 1885. He graduated from the Infantry Cavalry School at
Fort Leavenworth 1887. As a member of the
Oregon Alpine Club, he advocated for the exploration of Mount Olympus, which was finally permitted by General
John Gibbon. In summer 1890 O'Neil led the expedition and reached the summit of the southern peak on September 22, 1890. O'Neil was transferred to
Fort Custer in 1892. As a member of the
25th Infantry Regiment he participated in the
Spanish–American War and was stationed in
Cuba. Later assignments led him to the
Philippines and
Alaska. During General
Pershing's Pancho Villa Expedition O'Neil was stationed at the Mexican border. In 1916, he commanded the
21st Infantry Regiment, including its role during the
Panama–California Exposition. With the United States' involvement in
World War I in August 1917 Joseph O'Neil was promoted to
brigadier general of the
National Army. During World War I, he commanded the 179th Infantry Brigade, a unit of the
90th Division. After the war, he commanded the division before returning to the United States. He was returned to his permanent rank of
colonel and served until retiring in 1926. In 1930, the U.S. Congress passed legislation allowing World War I officers to retire at their highest wartime rank, and O'Neil was promoted to brigadier general on the retired list. ==Personal life==