Sullivan W. Gibson was either born on February 17, 1843, or January 19, 1845, in Warsaw, New York, to Daniel Gibson and Laura Morris. His father was a farmer and stove peddler who owned $900 of real estate and $390 of personal property by 1860. The family lived in Warsaw until the 1850s, when they moved to Grove, New York.
He enlisted in the Union army on October 17, 1861, and he mustered in as a private in Company A of the 104th New York Infantry. He was reportedly "stricken with pneumonia" during training, and he was discharged on May 24, 1862. He returned to the Union army in August 1862, mustering in as a private in Company D of the 1st New York Dragoons. The regiment took part in the Battle of Cold Harbor and the Appomattox campaign. He was promoted to corporal in May 1864.
In November 1864, he observed that “Lincoln is no doubt elected again for better or worse…The majority rules and I am satisfied though I fear the future is not all bright for my long suffering Country.” On April 9, 1865, he reported that “all at once firing ceased like lightning the news flew along the line that Lee had surrendered.” In the margins of his diary, he added that it was the “greatest day of my life for which I thank God. The Army is wild.” He mustered out on June 30, 1865.
He settled in Bellevue, Michigan, after the war, and he attended Olivet College in the 1870s. In 1874, he delivered a speech on Senator Charles Sumner. According to an early biographer, he “spent three years in [college] and was forced to discontinue his education because of weak eyes.”
He married a woman named Jennie around 1882, and they had three children: Carleton, born around 1883; Myra, born around 1885; and Mary, born around 1891. He earned a living as a farmer. He applied for a federal pension in July 1890 and eventually received one. His wife died in 1904, and he married Dora M. Ingersoll on February 8, 1913. He died of influenza in Bellevue on February 10, 1929.