Elmar A. Messinger was born on November 15, 1839, in Canton, Massachusetts, to Vernon and Adeline Messinger. His father was a silk manufacturer who owned $10,000 of real estate and $8,000 of personal property by 1860. The family lived in Canton until the 1850s, when they moved to Boston, Massachusetts. By 1860, Messinger was working as a clerk.
He enlisted in the Union army on May 26, 1862, and he mustered in as a private in Company A of the 4th Massachusetts Infantry Battalion the following day. He mustered out on May 31, 1862, “by proclamation of the President.” He returned to the Union army in August 1862, mustering in as a private in Company D of the 44th Massachusetts Militia Infantry. He expressed devotion to the Union, writing that, “when duty and a country calls one way and business another I can in a minute decide as I did between them and rank myself…among those who would for their country’s sake do and dare all.” He added that he could not “help thinking how thankful I am to have enlisted to do my duty as it calls me.” He eventually earned a promotion to corporal, and he mustered out on June 18, 1863.
Messinger returned to Boston after leaving the army, and he worked in the clothing industry. He married Sarah E. Wightman on January 26, 1871, and they had no children. He worked as an auditor and merchant in Boston. He applied for a federal pension in February 1907 and eventually secured one. He died in Boston on February 28, 1918.