When you sit down to your sumptuous feast this Thanksgiving, if you spare a thought or a prayer for those who brought you the holiday, make sure you’re remembering the right people. It was the Pilgrims, not those sour Johnnies-come-lately, the Puritans, who celebrated the first American Thanksgiving.

We confuse them all the time. I was reminded of this in rereading a classic of American historical writing, “Saints and Strangers,” by George F. Willison. This splendid amalgam of research and writing, first published in 1945 by Reynal & Hitchcock, reveals a lot of truths and puts straight a lot of errors concerning these ancestors of ours. Its full title gives a foretaste of the genial adventure the reader is about to embark upon: “Saints and Strangers: Being the Lives of the Pilgrim Fathers & Their Families, with Their Friends & Foes; & an Account of Their Posthumous Wanderings in Limbo, Their Final Resurrection & Rise to Glory, & the Strange Pilgrimages of Plymouth Rock.”

The Pilgrims were not Puritans. We’ll probably never get this right. My grandson’s dictionary, recently published, states, with all the boldness that only error can command: “The Pilgrims were Puritans.” The basic distinction is that many Pilgrims were Separatists from the Church of England, while the Puritans, though they did not like the church, at least maintained the polite fiction that they still were part of it. In fairness, it should be said that we come by our confusion honestly. The two groups did come to resemble each other in time. A smaller, weaker group, the Pilgrims of Plymouth, or Plimouth, Colony who arrived in 1620 on the Mayflower and subsequent ships eventually were absorbed by the Puritans of brash Massachusetts Bay Colony, who arrived later. But not before contributing much to Puritan culture, including religious doctrine: The Puritans — whose name, Willison tells us came not from their moral code but from their doctrine of “purifying” the established church — became Separatists.

The author says the Pilgrim saga as we know it — our errors, in other words — is of 19th-century origin, even the appellation “Pilgrim.” They called themselves the “First Comers,” or rather their descendants did.

The Pilgrim-Puritan confusion he lays at the feet of Henry Wadsworth Longfellow, himself of direct Pilgrim heritage, for mislabeling his heroes Puritans in his poem, “The Courtship of Miles Standish.”

There were other differences besides religion. The Pilgrims did not wear such drab clothing as the Puritans; Ruling Elder William Brewster even had “1 paire of greene drawers. “They liked good food and “strong waters.” Unlike Massachusetts Bay, Plymouth was never a pastor-ridden theocracy, nor did it ever hang a witch or a heretic. Plymouth’s rules governing sexual conduct were less severe.

Well, okay, Separatists, Puritans, Pilgrims, whatever — at least we know that all those who came over on the Mayflower were seeking religious freedom, right? No, says Willison, and hence his title. “Saints” were members of the Separatist church. “Strangers” were those who were not members, and they were by far in the majority. Miles, or Myles, Standish, perhaps the best known of the Pilgrim fathers, had a Roman Catholic background and never joined the Separatist church, though it is not likely he was Catholic himself.

All right, then, we do know that they sailed straight from Plymouth in England to Plymouth in the New World and that they were all good, solid, middle-class burghers who set up democracy straightaway. Correct? No, they sailed from the Netherlands, where they had spent several years in rancorous religious infighting. Saint or Stranger, they were all from the lower classes, some desperately poor.

The past is ironic prologue: The Dutch tolerance that allowed the Separatists to worship as they pleased also upset them because it tended to “corrupt” their children into non-Separatist ways. If the Saints sound similar to the Muslim “separatists” in the Netherlands today, then bear in mind that the Saints, when they got to Plymouth, formed a government only a little less exclusionary than the one they had fled in their native England.

Some things in our Pilgrim mythos, it turns out, are close to the facts. They almost starved to death for a couple of years, and without Squanto, that famous Indian who taught them much, they surely would have perished or been forced to flee. There was a first Thanksgiving — or harvest — feast, it was lavish, it went on for three days, and Indians attended, and while there may have been turkey on the table, there was definitely no pumpkin pie.

The facts are worth remembering, particularly those of the feast. The two sides rubbed along fairly well, the English realizing that the “savages” assured their survival and the Indians that they could use the English as allies. The Indians attended in part as a mark of respect, and oddly enough the feeling seems to have been mutual.

One could go on and on about this marvelous book. No doubt in the intervening six decades it has been superseded in some particulars, but it’s hard to believe that it has been in its general story and certainly not in its style. One of its delights is the extensive use of the Pilgrims’ and Puritans’ own words, replete with their idiosyncratic and inconsistent spellings. After a while you even begin to think that “ye” is the natural definite article. One of ye despairs of educators is that ye youngsters of today think that history is for ye birds. If ye educators could tell history like ye author does, ye kids might change their opinion.

Mr. Miller, a newspaperman for many years, is a freelance writer, reviewer, and editor.