William E. Vanauken was born around 1841 in Chemung County, New York, to John and Emeletta Vanauken. His father was a shoemaker. He grew up and attended school in Elmira, New York, and by the early 1860s, he was working as a clerk.
He enlisted in the Union army on August 7, 1862, and he mustered in as a private in Company D of the 107th New York Infantry later that day. According to his service records, he was 5 feet, 7 inches tall, with brown hair and blue eyes. The regiment took part in the Battle of Antietam, the Battle of Chancellorsville, the Battle of Gettysburg, and the Atlanta campaign. He was promoted to corporal on April 1, 1863, and to sergeant on March 5, 1864. He died in the Battle of New Hope Church on May 25, 1864.