Eugene L. Barnes was born around 1844 in Niagara County, New York, to George and Adaline Barnes. His father was a farmer who owned $4,500 of real estate and $1,000 of personal property by 1860. The family lived in Cambria, New York, until around 1854, when they moved to Ridgeway, New York. By the early 1860s, he was working as a farmer.
He enlisted in the Union army on August 6, 1862, and he mustered in as a private in Company A of the 151st New York Infantry on October 22 alongside his brother Romaine. According to his service records, he was 5 feet, 9 inches tall, with black hair and black eyes. The regiment took part in the Gettysburg campaign. On January 14, 1864, he was promoted to 2nd lieutenant of the 26th USCT Infantry. He eventually earned a promotion to 1st lieutenant. A year later, on March 30, 1865, he was promoted to captain in the 128th USCT Infantry. He later received a brevet promotion to major. He mustered out on October 31, 1866. He died in Louisiana on October 7, 1867.