Ezra S. Farnsworth was born around 1830 in Leominster, Massachusetts, to Asa and Lucy Farnsworth. He married Mary F. Brown on May 22, 1854, and they apparently had no children. They lived in Newton, Massachusetts, and Farnsworth worked as a real estate broker. By 1860, he owned $2,000 of real estate and $500 of personal property.
He enlisted in the Union army on July 14, 1862, and he mustered in as a sergeant in Company K of the 32nd Massachusetts Infantry. The regiment took part in the Second Battle of Manassas, the Battle of Antietam, the Battle of Fredericksburg, the Battle of Gettysburg, the Overland Campaign, and the siege of Petersburg. He was wounded at Gettysburg on July 2, 1863, but he eventually recovered and rejoined the regiment. He was promoted to 2nd lieutenant on March 19, 1863, to 1st lieutenant on June 15, 1864, and to captain on July 20, 1864. He mustered out on May 30, 1865.
Farnsworth returned to Newton after the war and earned a living as a real estate agent. He died of “hemiplegia” in Newton on April 2, 1886.