Walter Henry Wild was born on June 19, 1836, in Brookline, Massachusetts, to Charles and Mary Wild. His father was a physician who owned $20,000 of real estate by 1850. He grew up and attended school in Brookline, Massachusetts, and he attended Harvard University in the early 1850s.
He enlisted in the Union army on April 17, 1861, and he mustered in as a corporal in the 1st Rhode Island Light Artillery on May 2. He mustered out on August 6, 1861. He rejoined the Union army the following year, mustering into the 3rd Rhode Island Heavy Artillery. In March 1863, he was promoted to 1st lieutenant in Company K of the 54th Massachusetts Infantry. The regiment took part in the assault on Fort Wagner.
Then, in August 1863, he was promoted to captain in the 36th USCT Infantry. The regiment took part in the siege of Petersburg and the Appomattox campaign. He mustered out on August 14, 1866.
He married Helen M. Conklin in Texas on March 17, 1866, and they had at least two children: Ella, born around 1869; and Charles, born around 1876. The family lived in Springfield, Massachusetts, and he worked as a bookkeeper. He may have separated from his wife, as the 1870, 1880, and 1900 censuses all list the couple living separately. His wife died in 1907, and by 1910, he was living in his niece’s household in North Andover, Massachusetts. He died in 1922.