The Civil War was raging when Abraham Lincoln issued a presidential proclamation that started the process of making Thanksgiving, celebrated on the fourth Thursday of November, a federal holiday.
Previous presidents had issued Thanksgiving proclamations before. Washington had declared the first official national Thanksgiving in 1789. Lincoln himself had issued proclamations in the spring of 1862 and 1863, although those were days of thanksgiving for military victories. But the October 1863 proclamation was the first time that a president had singled out a specific date–the last Thursday in November–for the occasion of a holiday specifically called Thanksgiving.
Signed on October 3, 1863, just months after Union victory at the bloody Battle of Gettysburg, Lincoln’s proclamation declared that the wartorn nation’s year had nonetheless “been filled with the blessings of fruitful fields and healthful skies. To these bounties,” it continued, “which are so constantly enjoyed that we are prone to forget the source from which they come, others have been added, which are of so extraordinary a nature, that they cannot fail to penetrate and soften even the heart which is habitually insensible to the ever watchful providence of Almighty God.”
Despite being in the throes of “a war of unequalled magnitude and severity,” the country’s population was growing, business was booming and peace had been preserved with foreign powers (such as Britain) who might have joined the Confederate cause, it declared. That year, according to the White House Historical Society, the President began the tradition of pardoning a turkey in response to the pleas of his son Tad Lincoln. The next year’s Thanksgiving proclamation celebrated some of the same things–and noted the same "last Thursday in November" date.
Lincoln’s proclamation was “the culmination of a 36-year campaign started by so-called ‘mother’ or ‘godmother’ of Thanksgiving, Sarah Josepha Buell Hale,” writes Olivia B. Waxman for Time. Hale, who publicized and partially wrote the poem “Mary Had a Little Lamb,” was the “Lady Editor” of Godey’s Lady’s Book, a massively successful women’s magazine. Hale thought that the celebration, which was widely observed if not enshrined in law, “should be a national festival observed by all the people… as an exponent of our republican institutions.”
Using her editorial voice, Hale pushed for this aim and started a letter-writing campaign to government officials. Writing to Abraham Lincoln himself, Hale argued for the last Thursday in November, on the grounds that George Washington declared the first official national Thanksgiving on the last Thursday of November, 1789, writes Waxman.
In between that first official Thanksgiving and Lincoln’s proclamation, “subsquent presidents issued Thanksgiving Proclamations, but the dates and even months of the celebrations varied,” writes the National Archives. “Early Americans celebrated Thanksgiving not as a fixed annual event, but as a series of ad hoc holidays called in response to specific events,” writes Paul Quigley for The New York Times. “ These were religious occasions, intended to invoke God’s help to cope with hardships, or to offer God thanks for positive developments.”
However, Lincoln’s 1863 proclamation started something, the Pilgrim Hall Museum writes: an “unbroken string of annual presidential Thanksgiving proclamations” that stretched forward all the way to Franklin D. Roosevelt in 1941, when Congress passed a law fixing the date for Thanksgiving as the fourth Thursday in November. Presidents after Roosevelt continued to issue Thanksgiving proclamations but they were more formalities, since the holiday was now federal law. But because Lincoln’s 1863 declaration is what started it all, it's “regarded as the true beginning of the national Thanksgiving holiday,” the museum writes.