John Alexander Smith was born around 1832 in New York. He married Mary Lane on August 24, 1852, and they had three children: Julia, born on January 14, 1854; Mary, born on February 21, 1856; and William, born on September 21, 1859. They lived in New York City, New York, and he earned a living as a printer.
He received a commission as a 1st lieutenant in Company G of the 47th New York Infantry. According to his service records, he was 5 feet, 10 inches tall, with light hair and blue eyes. The regiment took part in the siege of Charleston, the Battle of Olustee, and the Bermuda Hundred campaign. He died in the Battle of Chester Station on May 7, 1864.