James O’Neil was born in 1838 in New York.
James left New York and had settled in western Michigan by 1860 when he was probably a news dealer living with and/or working for Bradley Salter, a saloon-keeper in Muskegon, Muskegon County.
James was 23 years old and probably still living in Muskegon when he enlisted in Company H on May 6, 1861. He was wounded in the right lung while the regiment was engaged in the Peach Orchard, during the second day of the battle of Gettysburg, on July 2, 1863, at Gettysburg, Pennsylvania, and subsequently died from his wounds on July 3 or 5 in one of the hospitals at Gettysburg.
In either case, he was buried in the Michigan plot, Gettysburg National Cemetery: section A, grave 8.
No pension seems to be available.