John L. Stilson was born around 1844 in Connecticut to Abel Stilson and Hannah Ambler. His father was a baker who owned $500 of personal property by 1850. They lived in Newtown, Connecticut, until the 1850s, when they moved to New York City. By 1860, he was also working as a baker.
He enlisted in the Union army on September 22, 1862, and he mustered in as a private in Company F of the 174th New York Infantry on November 5. According to his service records, he was 5 feet, 9 inches tall, with light hair and blue eyes. The regiment took part in the siege of Port Hudson. In February 1864, Union officials consolidated the 174th New York Infantry with the 162nd New York Infantry. The regiment took part in the siege of Petersburg, and he mustered out on December 12, 1864.
He returned to New York City after leaving the army, and he married Sarah E. Sickles. They had at least two children: Caroline, born around 1866; and Nellie, born around 1869. He worked as a book keeper, and by 1870, he owned $1,500 of personal property. In 1870, he pleaded guilty to grand larceny, and he was sentenced to one year at Sing Sing Prison. He died in Hartford, Connecticut, on March 3, 1875.