Nathaniel Low, Jr., was born on August 29, 1838, in Dover, New Hampshire, to Nathaniel to Mary Low. His father was a physician who owned $38,500 of real estate and $17,600 of personal property by 1860. The family lived in Rollinsford, New Hampshire, until the 1850s, when they returned to Dover. By 1860, Low was working as a merchant, and he owned $2,500 of real estate and $2,000 of personal property. He became a local postmaster in 1861.
He resigned a year later in order to join the Union army. He received a commission as a captain in Company K of the 11th New Hampshire Infantry on September 4, 1862. He resigned a month later, but he was eventually recommissioned as captain. He became a quartermaster sergeant on June 16, 1864, and he mustered out on February 2, 1866.
Low married Jennie Niles during the war, and they had at least two children: Lillie, born around 1869; and Etta, born around 1870. They settled in Memphis, Tennessee, after the war, and Low worked as a merchant and cotton broker there. They returned to New Hampshire in the 1870s. He applied for a federal pension in February 1890, but he died before he received it. He passed away of a “congestive chill” in New Hampton, New Hampshire, on May 1, 1890.