Franklin Sizer was born around 1840 in New York to Luther Sizer and Perlina Barnum. His father was a farmer who owned $9,000 of real estate and $120 of personal property by 1860. He grew up and attended school in Western, New York, and by 1860, he was working as a laborer on his father’s farm. He enlisted in the Union army on October 12, 1861, and mustered in as a private in Company I of the 81st New York Infantry on November 25. The regiment took part in the siege of Yorktown, the Battle of Seven Pines, and the Seven Days’ Battles. He died of disease in Yorktown, Virginia, on December 29, 1862.