According to progressive websites, Thanksgiving is a day devoted to arguing with your right-wing uncle. According to advertisements, it’s the day before Black Friday. In reality, it is the most American holiday.

It dates from before the establishment of the American nation-state and harkens back to our original settlers. Although the official holiday was formally established by the government and is marked by U.S. presidents, it has acquired its layers of meaning through religious faith, informal culinary and social customs, and a centuries-old vein of tradition — in other words, from the heart of the cultural nation.

After their brutal first winter in the New World, the Pilgrims — all 53 of them were survivors from the original Mayflower voyage — shared a feast with Wampanoag Indians in 1621. It wasn’t quite the picture-perfect gathering depicted in the famous, delightfully anachronistic Jennie Brownscombe painting of 1914 (complete with what looks like a golden-brown Butterball turkey), but notable all the same.

Their meal was very different from ours, with seafood and venison occupying an important place (the Indians killed five deer). They also certainly ate birds. One of the participants in the feast, Edward Winslow, wrote a letter to a friend describing how “our governor sent four men on fowling, so that we might rejoice together.”

Technically, the Pilgrims’ celebration was a harvest feast, rather than what they would have understood as a day of thanksgiving, which would have involved fasting and supplications to God. In time, the New England Colonies established annual general thanksgiving days not occasioned by any specific event, although they, too, were solemn occasions. From these sources, as Melanie Kirkpatrick explains in her engaging book on the holiday, Thanksgiving as we know it arose.

It is a thread that runs throughout American history. In 1778, the Continental Congress designated Dec. 30 “to be observed as a day of public thanksgiving and praise, that all the people may, with united hearts, on that day, express a just sense of his unmerited favors.” George Washington made the first presidential proclamation in 1789, urging gratitude, among other things, “for the signal and manifold mercies, and the favorable interpositions of his providence, which we experienced in the course and conclusion of the late war — for the great degree of tranquility, union, and plenty, which we have since enjoyed.”

In 1863, Abraham Lincoln declared a national day of thanksgiving — designating it as the last Thursday of November — and every president has done the same since with some occasional deviations as to the exact day.

Even the connection of the holiday to football stretches back to a Princeton-Yale game in 1873, which became an annual tradition in New York City. Colleges and high schools scheduled rivalry games for the day.

The holiday is associated in the American imagination — and, in fact — with the ingathering of family and with warmth and plenty. The widely reproduced George Durrie painting from 1863, “Home to Thanksgiving,” depicts a couple returning to a snow-covered farm for the holiday and getting greeted by an older couple at the door of the house, welcoming them back to hearth and home. The even more famous Norman Rockwell painting from 80 years later, “Freedom From Want,” might as well be the continuation of the Durrie scene, now indoors. An elderly couple serves a big, juicy bird to a beaming family. (Rockwell painted the turkey from a real model, soon consumed, on Thanksgiving Day.)

For most Americans, the day functions as the great 19th-century promoter of the holiday, Sarah Josepha Hale, hoped it would. “Such social rejoicings,” she wrote in 1857, “tend greatly to expand the generous feelings of our nature, and strengthen the bond of union that finds us brothers and sisters in that true sympathy of American patriotism.”

As long as there’s been America, there’s been Thanksgiving, calling us home and eliciting our fellow-feeling, at least for a day.

Rich Lowry is on Twitter @RichLowry.