Frederick S. Barnard was born on March 22, 1843, in Maine to George and Frances Barnard. His father was a trader who owned $300 of personal property by 1860. He grew up in Calais, Maine. He enlisted in the Union army on December 16, 1861, and he mustered in as a private in Company K of the 15th Maine Infantry. The regiment was stationed in the Department of the Gulf until July 1864, when it joined the Army of the Shenandoah.
Barnard was promoted to sergeant sometime in 1862, and he mustered out on January 19, 1865. He returned to the Union army soon afterward, receiving a commission as a captain in Company G of the 14th Maine Infantry on March 15, 1865. He mustered out on August 28, 1865.
He returned to Maine after the war, and he married Laura Merrill. Their daughter Corinne was born around 1871. They moved to St. Louis, Missouri, and his wife died there on December 17, 1872. Barnard then moved to Jackson County, Illinois, and he married Samantha F. Hindman on June 2, 1874. He died during the winter of 1874-1875.