John Low Smith was born around 1837 in Scotland to John and Mary Smith. He immigrated to America around 1844 and settled in Andover, Massachusetts, and by the late 1850s, he was working as an ink maker. He married Mary E. Barker in Lawrence, Massachusetts, on September 16, 1859, and they had at least three children: David, born around 1860; George, born around 1869; and Charles, born around 1870. By 1860, they owned $50 of personal property, and they employed a white domestic servant.
He enlisted in the Union army on August 8, 1862, and mustered in as a private in Company I of the 35th Massachusetts Infantry on August 16. The regiment took part in the Battle of Antietam, the Battle of Fredericksburg, the siege of Vicksburg, the Knoxville campaign, the Overland Campaign, the siege of Petersburg, and the Appomattox campaign. He was promoted to sergeant and then to 2nd lieutenant. He mustered out in Alexandria, Virginia, on June 9, 1865.
Smith returned to Andover after the war and earned a living as a merchant. By 1870, he owned $7,000 of real estate and $2,500 of personal property. A decade later, he was working as a grocer. His wife died around 1890, and he married Ella Florence Merrill on September 6, 1893. He died in Andover on March 14, 1917.