Nahum H. Farmer was born on January 24, 1843, in Sterling, Massachusetts, to Emory and Sophia Farmer. His father was a farmer who owned $4,500 of real estate and $500 of personal property by 1860. They lived in Sterling until the 1850s, when they moved to Harvard, Massachusetts.
He enlisted in the Union army on August 14, 1862, and he mustered in as a private in Company G of the 36th Massachusetts Infantry on August 27. According to his service records, he was 5 feet, 7¾ inches tall, with sandy hair and blue eyes. The regiment took part in the Battle of Fredericksburg, the siege of Vicksburg, the Knoxville campaign, the Overland Campaign, the siege of Petersburg, and the Appomattox campaign. He earned a promotion to corporal in the summer of 1864, and he mustered out on June 8, 1865.
He settled in Worcester, Massachusetts, after the war, and he married Ella Whittemore on July 18, 1866. They had at least two children: Grace, born around 1870; and Walter, born around 1879. They lived with Ella’s mother Elizabeth in Worcester, and Farmer worked in a shoe shop. He applied for a federal pension in October 1891 and eventually secured one. By 1900, he was working as a janitor. His wife died in 1909, and he passed away in Worcester on February 4, 1917.