The event we now know as "the First Thanksgiving" was in fact neither the first occurrence of our modern American holiday, nor was it even a 'Thanksgiving" in the eyes of the Pilgrims who celebrated it. It was instead a traditional English harvest celebration to which the colonists invited Massasoit, the most important sachem among the Wamapanoag. It was only in the nineteenth century that this event became identified with the American Thanksgiving holiday.

The association of the Pilgrims with the Thanksgiving holiday has a complicated history. The holiday itself evolved out of a routine Puritan religious observation, irregularly declared and celebrated in response to God's favorable Providence, into an single, annual, quasi-secular New England autumnal celebration. The first national Thanksgiving was declared in 1777 by the Continental Congress, and others were declared from time to time until 1815. The holiday then reverted to being a regional observance until 1863, when two national days of Thanksgiving were declared, one celebrating the victory at Gettysburg on August 6, and the other the first of our last-Thursday-in-November annual Thanksgivings. Although the Pilgrims' 1621 harvest celebration had been identified as the first American Thanksgiving as early as 1841 by Alexander Young, the common Thanksgiving symbolic associations in the 19th century centered on turkeys, Yankee dinners and an annual family reunion, not Pilgrims. The now famous 1621 event had been in fact entirely forgotten until the 1820s, when the full text of Mourts Relation (1622) with the reference to the feast was rediscovered. Mention of the Pilgrims brought the Landings or Myles, Priscilla, and John to mind, not Thanksgiving.

Moreover, whenever a Pilgrim, or more accurately, a generic 17th-century puritan image appeared in popular art in connection with Thanksgiving during the nineteenth century, it was not the now familiar scene of English and Indians sitting down to an outdoor feast. On the contrary, the image almost always portrayed a violent confrontation between colonist and Native American. It was only after the turn of the century, when the western Indian wars were over and the "vanishing red man" was vanishing satisfactorily, that the romantic (and historically correct) idyllic image of the two cultures sitting down to an autumn feast became popular. By the First World War, popular art (especially postcards), schoolbooks and literature had linked the Pilgrims and the First Thanksgiving indivisibly together, so much so that the image of the Pilgrim and the familiar fall feast almost ousted the Landing and older patriotic images from the popular consciousness. This alliance also deflated Forefathers' Day, which sank in to insignificance even in Plymouth itself.