As the Civil War’s first Christmas neared, a pair of young lovers, Nathaniel Dawson and Elodie Todd, a Confederate soldier and his eventual bride, wrote to one another with increasing melancholy. They were separated by hundreds of miles, and their communication was often interrupted by delays in the mail and the desperation of the Civil War.

“I wish I could be with you at Christmas, the festal season, where age is rejuvenated and lives again in the merry carols of youth,” Dawson wrote to Todd (sister of Mary Todd Lincoln) on December 22, 1861. On the holiday itself, he wrote to describe his regiment’s rowdy celebrations. “Bad whiskey is abundant and pleasure and sorrow drowned in large potations,” he said.

Dawson and Todd’s lives changed dramatically during the war, as the Confederacy crumbled and their personal lives stretched to their limits. But they weren’t alone in wishing they could celebrate Christmas together. As the fractured United States fought, the holiday took on new meaning.

By the end of the war in 1865, Christmas had gone from a relatively unimportant holiday to the opposite—a day rooted in an idealized vision of home. The way Americans observed the holiday changed too, setting the stage for the more modern Christmas holiday we know today.

Before the Civil War, Christmas was not an official holiday in the United States. Nor was it celebrated uniformly across the country. In early New England, Christmas was looked down upon by Puritans and Calvinists, who felt the day should be observed for strict fasts and rituals, if it was observed at all. During the 17th century, Massachusetts imposed a fine on colonists who celebrated the holiday, and after it became a state, its businesses and schools did not observe the holiday at all.

Elsewhere, Christmas was celebrated in a variety of ways, most depending on the country of origin of the immigrants who celebrated it. But by the mid-19th century, the holiday’s importance—and distance from religious tradition—was already starting to grow. Songs and carols like “Jingle Bells” (1857) and poems like “A Visit from St. Nicholas” (1823) set the stage for a fun, secular holiday that revolved around gift-giving and celebration with food and drink.

In the antebellum South, plantation owners used the holiday as a way to show off their paternalism toward the people they enslaved, write historians Shauna Bigham and Robert E. May. During lengthy Christmas celebrations, they gave enslaved people passes to marry, provided food and alcohol, and gave gifts.

Though enslaved people managed to create some of their own Christmas traditions, many of which incorporated traditions from Africa, they were also expected to help absolve slaveowners’ guilt over the holidays by enthusiastically opening gifts and showing their gratitude. “So far as their owners could tell,” Bigham and May write, “most slaves played their prescribed role to the hilt throughout the holiday.”

But the Civil War disrupted not just the relations between plantation owners and the people they enslaved, but those within families and communities. As both sides shifted their resources to war, the ability to give gifts and celebrate was dramatically curtailed. People cast their decision to have more modest Christmas celebrations as a patriotic one, and children got in on the act, too. Instead of giving and receiving store-bought gifts, they made more humble gifts like popcorn balls or crude homemade toys. And they learned to temper their expectations of Santa.

One Confederate family's children were told "not to expect a visit from St. Nick because the Yankees had shot him,” writes historian James Alan Marten, “while other parents offered more sensitive explanations. As a Yankee, Santa would be held up by Confederate pickets or perhaps Union blockading vessels had interrupted his journey.”

Meanwhile, those children’s mothers, aunts and sisters experienced Christmas as an agonizing reminder of the danger faced by men who had gone to war. Civil War-era diaries and letters document how many women felt anxiety, grief and depression around Christmas.

In 1861, Margaret Cahill wrote to her husband, Thomas, a Union officer, that she felt so “nervous and lonely” that she could not write to him on Christmas. “Will you say? Why did you not write to me on Christmass [sic] Day” she wrote. “Well to tell you the truth I was not able.” “Never before had so sad a Christmas dawned upon us,” wrote Sallie A. Brook, a Confederate woman from Richmond, of Christmas 1861.

On the battlefield, men on both sides tried to celebrate Christmas by giving gifts, eating and drinking, and taking time off. In his memoir, James A. Wright, a sergeant in the First Minnesota Volunteer Infantry Regiment, recalls eating beef soup and greeting his fellow soldiers on Christmas in camp. “The men had been allowed as much liberty as consistent with discipline and were ‘circulating around’ among their acquaintances in other regiments,” he recalled. “I was frequently invited to ‘smile,’” or take a drink. In 1863, a Confederate soldier from North Carolina wrote to his mother asking for a bottle of brandy and some sugar so he could make eggnog for his fellow soldiers.

Popular media did its best to increase the morale of both soldiers and their families at home around Christmas. Harper’s Weekly, the most popular periodical at the time, published a variety of Christmas stories and illustrations during the war. The most famous were drawn by illustrator Thomas Nast, who portrayed not just sad wives and husbands but happy Christmas Day traditions. He is credited with solidifying how the nation imagined Santa Claus with illustrations of a jolly, bearded St. Nick who handed out good cheer to soldiers and families alike.

Though individual traditions still varied, the upheaval of the Civil War made the holiday seem more and more important to separated families. “The Christmas season [reminded] mid-19th century Americans of the importance of home and its associations, of invented traditions,” writes historian David Anderson.

When the war ended, the magazines and newspapers that had underlined the importance of the holiday kept promoting it, and reunited families, devastated by the losses of the war, kept cherishing it. In 1870, in the aftermath of the war, Congress passed the first federal holiday law and made Christmas an official holiday. Four years of war had changed the holiday from a loose celebration to an essential one.