John R. Hart was elected Captain of the "Sardis Volunteers" from Floyd County GA, enlisting on June 24, 1861. This company served as Co. "E", 21st Georgia Regiment in Virginia until detached by S.O. 106, May 8, 1862, and assigned to Col. Sumner J. Smith's Georgia Legion. On the return to Georgia, Capt. Hart's command was mounted and designated Co. "G", Smith's Georgia Legion.

In 1860 John R. Hart lived in North Carolina District, Coosaville, Floyd County GA, with wife Agnes and children Virginia and Miles. All except Agnes were born in North Carolina, she being born in Virginia. In 1850 John, Agnes and newborn Virginia appear in Granville County NC. Although the age for John R. Hart should be 29 and he is registered as 20, this could be a copyist error on the census manuscript.