WILKESBORO, N.C.—Each month, Irene Triplett collects $73.13 from the Department of Veterans Affairs, a pension payment for her father’s military service—in the Civil War. More than 3 million men fought and 530,000 men died in the conflict between North and South. Pvt. Mose Triplett joined the rebels, deserted on the road to Gettysburg, defected to the Union and married so late in life to a woman so young that their daughter Irene is today 84 years old—and the last child of any Civil War veteran still on the VA benefits rolls.

Ms. Triplett’s pension, small as it is, stands as a reminder that war’s bills don’t stop coming when the guns fall silent. The VA is still paying benefits to 16 widows and children of veterans from the 1898 Spanish-American War. The last U.S. World War I veteran died in 2011. But 4,038 widows, sons and daughters get monthly VA pension or other payments. The government’s annual tab for surviving family from those long-ago wars comes to $16.5 million. Spouses, parents and children of deceased veterans from World War II, Korea, Vietnam, Kuwait, Iraq and Afghanistan received $6.7 billion in the 2013 fiscal year that ended Sept. 30. Payments are based on financial need, any disabilities, and whether the veteran’s death was tied to military service. Those payments don’t include the costs of fighting or caring for the veterans themselves. A Harvard University study last year projected the final bill for the Iraq and Afghanistan wars would hit $4 trillion to $6 trillion in the coming decades.

Eric Shinseki, the secretary of Veterans Affairs, often cites President Abraham Lincoln’s call, in his second inaugural address, for Americans “to care for him who shall have borne the battle and for his widow and his orphan.” “The promises of President Abraham Lincoln are being delivered, 150 years later, by President Barack Obama, ” Secretary Shinseki said in a speech last fall. “And the same will be true 100 years from now—the promises of this president will be delivered by a future president, as yet unborn.” A declaration of war sets in motion expenditures that can span centuries, whether the veterans themselves were heroes, cowards or something in between.

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Ms. Triplett’s father, Pvt. Mose Triplett, was born in 1846, on the mountainous Tennessee border in Watauga County, N.C. He was 16 years old when he got caught up in the fratricidal violence of the Civil War. North Carolina seceded from the Union soon after Confederate forces attacked federal troops at Fort Sumter, S.C., on April 12, 1861. Confederate records show Pvt. Triplett joined the 53rd North Carolina Infantry Regiment in May 1862. He spent half of that enlistment hospitalized, though records aren’t clear whether for illness or a gunshot wound to the shoulder that he suffered at some point during the war. In January 1863, Pvt. Triplett transferred to the 26th North Carolina Infantry Regiment. The regiment’s farmers, tradesmen and mountain men were commanded by 20-year-old Col. Henry Burgwyn, Jr., a strict drillmaster educated at the Virginia Military Institute, according to David McGee’s regimental history. Earlier, in 1859, Col. Burgwyn had been one of the VMI cadets dispatched to provide security at the hanging of John Brown, the famous abolitionist.

Col. Burgwyn’s martinet ways alienated his men at first. But he won their affection and a reputation for coolness under fire when he guided the regiment across a swollen river after the Southern defeat at New Bern, N.C. The regiment spent months sparring with Federal forces. In June 1863, the men were posted outside Fredericksburg, Va., trading artillery rounds with Union troops across the Rappahannock River. On June 15, the North Carolinians began the long march through the Shenandoah River Valley, across a slice of Maryland and into Gettysburg, Pa. Gen. Robert E. Lee intended to give the North a taste of the war, fought so far mostly on Southern soil.

Along the way, Pvt. Triplett fell ill with fever and went to a Confederate hospital in an old tobacco warehouse in Danville, Va. Eight days later, he disappeared. Pvt. Triplett was “present or accounted for until he deserted on June 26, 1863,” state records say. He missed a terrible battle for his regiment, and the South, whose loss at Gettysburg portended its final defeat. Of the regiment’s 800 men who fought at Gettysburg, 734 were killed, wounded or captured. There was a strong strain of Union sympathy in western North Carolina. Friendly locals often helped hide Confederate deserters. Pvt. Triplett crossed the mountains to Knoxville, Tenn., where on Aug. 1, 1864, he joined a Union regiment, the 3rd North Carolina Mounted Infantry. Military records listed him as a farmer, 5 feet 8 inches, blue eyes and sandy hair. He signed his enlistment contract with an X. An Army surgeon certified him “free from all bodily defects and mental infirmity, which would in any way disqualify him from performing the duties of a soldier.” The recruiting officer swore that Pvt. Triplett was “entirely sober when enlisted.” Pvt. Triplett’s older brother, Darby, joined the same day. “He served his time out with the Union so he would get a pension,” said Pvt. Triplett’s grandson, Charlie Triplett, of North Wilkesboro, N.C.

Pvt. Triplett’s Union regiment was nicknamed ” Kirk’s Raiders,” after its daring, Tennessee-born commander, Col. George Washington Kirk. Col. Kirk, a carpenter, rocketed from private to commander of a regiment he assembled from Union supporters in western North Carolina and eastern Tennessee. Pvt. Triplett’s new regiment slipped in and out of North Carolina to destroy Confederate supply depots, railroads, and bridges in the region where Pvt. Triplett grew up, according to a history by Matthew Bumgarner.

At times, Col. Kirk’s men took food from Confederate sympathizers to give to Union sympathizers. Union commanders praised Col. Kirk for his derring-do. Confederates saw him and his men as little more than hooligans and turncoats. The war came to a close after Gen. Lee’s surrender at Appomattox Court House, Va., on April 9, 1865. Pvt. Triplett was discharged four months later. Military records show he owed the government $129.99 for uniforms and other gear, offset by a $100 enlistment bonus the Army owed him. Back home, tensions simmered between those who had sided with the Confederacy and those who joined Union forces, especially a regiment as hated as Kirk’s Raiders. “Most, if not all, of these soldiers would be outcasts, to a degree for the remainder of their lives,” Ron V. Killian wrote in his history of the 3rd North Carolina Mounted Infantry. In 1885, Pvt. Triplett applied for a pension and, apparently impatient with the delay, had his congressman submit legislation the following year to approve his request, a common practice. The bill died, but records suggest Pvt. Triplett eventually secured a Union pension of unknown size.

Pvt. Triplett had farmland and a big house near Elk Creek, in Wilkes County, N.C. Long after his death, local men would drink moonshine, play banjo and fiddle, and swap legends about what a “hard man” Mose Triplett had been, said his grandson, Charlie Triplett, who heard the stories from his father. He wore a Wyatt Earp mustache and would pull the fangs from rattlesnakes, then keep them as pets in a chicken coop. “A lot of people were afraid of him,” Charlie Triplett said. “Most of the time he sat on the front porch with his old military pistol and shot walnuts off the trees just to let people know he had a gun.” Once, standing atop a car in the center of Wilkesboro, Pvt. Triplett cursed a local bank that had gone under and taken his money with it. “He was a cussing just like a preacher would preach,” Charlie Triplett said. Pvt. Triplett and his first wife, Mary, apparently had no surviving children, according to a review of decades of census records. After Mary Triplett’s death in the 1920s, Pvt. Triplett married Elida Hall, nearly 50 years his junior. She was a distant relation of Thomas Dula, whose 1868 hanging for his girlfriend’s murder was recounted in the folk song ” Tom Dooley, ” which was made popular by the Kingston Trio in a 1958 recording. Such May-December marriages weren’t uncommon. Jay Hoar, a Civil War researcher, found 72 couples where the age difference between the veteran and his wife was at least 19 years. The biggest spread was between a 93-year-old Virginia cavalryman and his 26-year-old bride.

Many of the marriages took place during the Great Depression, when veterans’ pensions offered some financial security. About a third of the wives were nurses, offering security for aged veterans, as well, according to Mr. Hoar. Elida Hall’s 1924 marriage doesn’t appear to have been so blessed. She was mentally disabled, according to people who knew her. The couple lost three babies—Phema, Patsy, and Billie Coolidge. Irene was born in 1930 when her father was age 83 and her mother 34. Irene, too, suffered from mental disabilities, said past and current nursing home staff. Pvt. Triplett was just shy of his 87th birthday when Elida gave birth to a son, Everette, later the father of Charlie Triplett. Irene and Everette Triplett were born in tough country during tough times. The forested hills ran with white lightning from illegal stills. Ms. Triplett said she didn’t drink moonshine, but she got hooked on tobacco in first grade. “I dipped snuff in school, and I chewed tobacco in school,” said Ms. Triplett, who lives in a nursing home in Wilkesboro. “I raised homemade tobacco. I chewed that, too. I chewed it all.” Irene said her teachers beat her with an oak paddle. Her parents continued the beatings at home, she said: “When you got a whooping in school you’d be getting tore up when you got back in those mountains.” At school, children would taunt Irene about her father the “traitor,” said Charlie Triplett. She dropped out after sixth grade, unable to read or write proficiently. Of her parents, she said, “I didn’t care for neither one of them, to tell you the truth about it. I wanted to get away from both of them. I wanted to get me a house and crawl in it all by myself.”

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In 1938, on the 75th anniversary of the Battle of Gettysburg, the government paid for Civil War veterans from both sides to attend a reunion on the Pennsylvania battlefield. Pvt. Triplett was one of more than 1,800 who went. “Lincoln spoke in solace for all who fought upon this field; and the years have laid their balm upon their wounds,” President Franklin Roosevelt told them. “Men who wore the blue and men who wore the gray are here together, a fragment spared by time.” Pvt. Triplett wore both, but he kept that secret during the reunion. Organizers housed him in the Confederate camp. The Gettysburg Times quoted him saying he had “fooled everybody” because he had actually been in the Union Army for the entire war, a tale at odds with his military records.

“We didn’t want to leave the Union,” Pvt. Triplett told the newspaper, “but our neighbors did.” Pvt. Triplett died of cancer days after returning from Gettysburg, at age 92. His family put pennies on his eyes and buried him on a hillside covered in holly, pine, oak and cedar.

In Wilkes County, the local Sons of Confederate Veterans of the Civil War put Confederate flags on tombstones of rebel soldiers. Mose Triplett’s granite grave marker has no flag and is conspicuous in its neutrality. “He was a Civil War soldier,” it reads. In 1943, 13-year-old Irene and her mother, unable to fend for themselves, moved into the Wilkes County poorhouse. Locals remember it as a grim, two-story brick building on the outskirts of town, where mice and rats scampered on concrete floors.

The complex also had a wood frame “TB hut” for tuberculosis patients, as well as a two-room “colored ward” that doubled as a jail for blacks, according to a 1946 county insurance report. Though just 10 years old, Irene’s brother, Everette, ran away rather than live there, Charlie Triplett said. Everette Triplett made his way to Roxboro, N.C., and found work in a saw mill. He became a bulldozer operator and died in 1996. Irene and Elida Triplett remained at the county home for 17 years. The facility shut down in 1960, and Irene and her mother moved into a new private nursing home. The women didn’t get along and had to have separate rooms, recalled James Richardson, one of the nursing home founders. “I didn’t play around,” Irene Triplett said. “I mowed the grass. I washed dishes, made up beds, washed and ironed. They had hogs. They raised hogs up there. I raised eight hogs.” Once a month, the two women would put their X marks on the VA pension checks, which helped pay for their care. At one point, Irene’s brother, Everette, invited her to live with him, but she had grown accustomed to institutional life and declined, Charlie Triplett said. Elida Triplett died of cancer in 1967. Irene Triplett lived in the nursing home for more than half a century until she broke her hip last year and moved into the Wilkesboro skilled-nursing facility. Medicaid pays her expenses at the home, supplemented by the VA pension her father earned her in 1865. She said she likes the facility more than anywhere else she has lived. She gets very few visitors, but enjoys working on crafts and watching TV. She attends religious services. She inches her wheelchair through the halls. Sociable but prone to bouts of isolation, she often spends her time in the lobby, sipping a Coke and spitting tobacco through a toothless smile.

  Write to Michael M. Phillips at michael.phillips@wsj.com