Sylvester H. Stevens was born around 1840 in East Brookfield, Massachusetts, to Ezekial and Tammy Stevens. His father was an innkeeper who owned $3,500 of real estate by 1850. He grew up and attended school in North Brookfield, Massachusetts, and by 1860, he was working as a laborer.
He enlisted in the Union army on September 19, 1861, and he mustered in as a private in Company I of the 24th Massachusetts Infantry four days later. He was wounded in the Battle of Darbytown Road on October 13, 1864, but he eventually recovered and rejoined the regiment. He mustered out on January 20, 1866.
He returned to East Brookfield after the war, and he worked in a wheel shop. He died of chronic diarrhea in East Brookfield on October 15, 1907.