William Wilson was born on December 23, 1844, in Hanover, New York, to James and Philena Wilson. His father was a farmer who owned $3,700 of real estate and $600 of personal property by 1860. He grew up and attended school in Hanover, and by the early 1860s, he was also working as a farmer.
He enlisted in the Union army on August 30, 1862, and he mustered in as a private in Company K of the 112th New York Infantry on September 11. He apparently lied about his age, claiming that he was 18 years old. According to his service records, he was 6 feet 1 ½ inches tall, with brown hair and light eyes. The regiment took part in the siege of Suffolk, the Battle of Cold Harbor, and the siege of Petersburg. He was promoted to corporal in September 1864. He was wounded in the Battle of Chaffin’s Farm in September 1864, and he died on November 5, 1864.