William W. Fish was born on January 15, 1843, in North Chelmsford, Massachusetts, to John and Mary Fish. His father was an iron founder who owned $1,000 of real estate by 1850. The family lived in Lowell, Massachusetts, until the 1850s, when they moved to Manchester, New Hampshire.
He enlisted in the Union army on August 8, 1862, and he mustered in as a private in Company C of the 11th New Hampshire Infantry on August 21. The regiment took part in the Battle of Fredericksburg, the siege of Vicksburg, the Overland Campaign, and the siege of Petersburg. He was wounded at Fredericksburg on December 13, 1862, but he eventually recovered and rejoined the regiment.
He denounced northern Peace Democrats, writing that he “would like to see such men drafted and put into the field.” When an acquaintance “voted the Copperhead ticket” in March 1863, Fish declared that he should “go to Jeff Davis’s dominions if he likes them better than he does our Government.” Confederate forces captured Fish in the Battle of the Wilderness on May 6, 1864, and he remained a prisoner of war until December 13, 1864. He reportedly had “both legs broken by [a] collision while on [the] way home,” and he was discharged for disability on July 31, 1865.
He married Eliza Gage around 1869, and they had at least two children: Abigail, born around 1872; and Milton, born around 1875. They lived in Somerville, Massachusetts, and Fish worked as a Custom House clerk. By 1900, he was working as a real estate agent. His wife died in 1917, and he married Helen L. Stevens on May 15, 1919. They lived in Mount Vernon, New Hampshire, and Fish died in August 1936.