John Newton Carnahan, son of John A. and Elizabeth Bailie Carnahan, was born on December 29, 1824, in an area of Wythe County, Virginia that later became part of Pulaski County. On March 4, 1845, Carnahan married Juliette Sophia Calfee (1826-1909). The couple had six children (Margaret, Edwin, John A., Mary Ellen and Letitia P.) and owned a farm on the south side of the New River.

During the American Civil War Carnahan enlisted in Company F, 54th Virginia Infantry of the Confederate Army at Newbern, Virginia on September 9, 1861. He seems to have remained with the regiment until he fell ill in Russell County, Virginia the following spring. Family tradition holds that Juliette brought her husband to the family's Pulaski County home, where he died on July 25, 1862. (Curiously, however, Carnahan's published obituary states that he died in Russell County.)

The 54th Virginia Infantry of the Confederate Army was organized by Colonel Robert C. Trigg in Southwest Virginia during the late summer and early fall of 1861 during the American Civil War. Mustered into service on September 10, the regiment trained at Camp Hall in Montgomery County before joining the Army of Eastern Kentucky. The 54th participated in battles at Middle Creek (Kentucky) and Princeton ((West) Virginia) in 1862, then returned to Southwest Virginia for several months before being ordered east late in the year. The regiment participated in the Battle of Kelly's Store in January 1863, then was transferred to the Army of East Tennessee. The 54th saw action at the battles of Chickamauga and Missionary Ridge before participating in Johnston's Atlanta Campaign and Hood's Tennessee Campaign in 1864. Afterward, Trigg and a detachment returned to Southwest Virginia, while the remainder of the regiment found itself participating in the Carolina Campaign at war's end.