Why do we still need Black History Month? On its first day alone, this February provided two good answers. One is that we need it because our president and his spokesman seem to have no idea who Frederick Douglass was or even that he is not currently alive. But a second is that, mysteriously, it seems a large number of Americans believe that the inventor of the cotton gin, Eli Whitney, was black.

This became a topic of chatter online on Wednesday when Rembert Browne, a writer-at-large for New York magazine, tweeted about it:

yearly reminder that half the country was incorrectly taught that eli whitney was black — Rembert Browne (@rembert) February 1, 2017

He was quickly deluged with confirmations that this is indeed a thing:

I had to do a presentation on him for BHM in 5th grade. I was so damn confused... https://t.co/isr7BzqOGq — Keith RC (@kreid_c) February 1, 2017

I remember being taught this in public elementary school in Chesapeake, VA — Ellie Hall (@ellievhall) February 1, 2017

@jbouie @ellievhall @rembert This was taught in my elementary school in suburban Kentucky. Didn't find out otherwise till HS in Boston. — Polly Mosendz (@polly) February 1, 2017

What’s going on? First things first: Whitney was white. He is not a mysterious figure. He was born in 1765 in Massachusetts to a wealthy farming family, he went to Yale, he married Jonathan Edwards’ granddaughter, and he died in 1825. Portraits composed during his own lifetime confirm that he was, indeed, a white guy.

But it appears that thousands, maybe millions, of Americans have grown up believing otherwise. There seems to be no geographical locus for the misinformation. Commenters from Georgia, California, Kentucky, Indiana, Ohio, Virginia, Kansas, Florida, and Massachusetts insisted online on Wednesday they had been taught in school that Whitney was black. Older examples of this conviction are as plentiful as cotton bolls on a Georgia plantation: Here’s a woman indignant that Ball Park depicted Whitney as white in a TV ad. “Eli Whitney was a slave,” writes a contributor to a forum on black issues. “Name five important black people from history beside Rosa Parks, MLK Jr., Eli Whitney or Malcolm X,” a Reddit contributor requests. On another Reddit thread, commenters commiserate over their shared false memory of Whitney’s race. As of this writing, 55 percent of respondents to a BuzzFeed poll posted Wednesday say they have always believed Whitney was black. “I always knew he was white, but I always knew people who thought he was black,” says Chris Hartig, who took this photo of a poster in his Illinois high school back in 2012:

If they did believe in Whitney as a black hero of invention, it might be because plenty of authoritative sources told them as much. For example, here’s a Head Start classroom in February 1990 learning about “Black people from history” including Martin Luther King Jr., Willie Mays, and Whitney. The 1989 KRS-One song “You Must Learn,” an anthem on education and empowerment, lists Whitney among black inventors such as Garrett Morgan and Madame C.J. Walker. The video shows black men turning bales of cotton, over the mention of Whitney’s name.

Bill Brown, the director of the Eli Whitney Museum and Workshop in Hamden, Connecticut, says that he has often heard the notion that Whitney was black. “It’s always difficult to link a legend to a source,” he told me by email. But several good guesses exist as the origin of the myth.

For one, Whitney’s invention was so tangled up in black history that it is often taught during Black History Month in elementary school history classrooms and other sites of popular history. Patented in 1793, the cotton gin turned a labor-intensive crop into an extremely profitable one, boosting the demand for slave labor. Between 1790 and 1860, the number of slave states grew from eight to 15, and the slave population more than quintupled in the same period.* A Florida newspaper’s 1994 bullet-point list of “How Black Americans Helped Shape the Sunshine State,” for example, has one entry that reads “1793: Eli Whitney’s cotton gin leads to increased importation of slaves to work on cotton plantations.” It’s not claiming Whitney was black, but it’s understandable how a casual reader could interpret it that way.

Since Whitney’s race is so well-established, it seems unlikely that textbooks exist with the explicit claim that Whitney was black—in any case, I was unable to locate any. (If you have evidence otherwise, email me.) But the fact that black inventors are a unit in many grade-school Black History Month curricula makes the mistake imaginable. If students are learning about George Washington Carver, Garrett Morgan, and Lewis Latimer along with broader black history, mistakes will be made. (I knew Whitney was white, but I remember confusing Carver and Jimmy Carter as a child: both famous Southerners with peanut-related stories and similar last names. And until I Googled Carver just now, I could have sworn he was from Georgia.) It can’t help that black inventor Elijah McCoy, son of fugitive slaves, has a similar name. (Some people insist Whitney’s name sounds black, and that’s what causes the confusion.) Meanwhile, there’s another commonly repeated legend that Whitney got the idea for his invention from a slave. All of these factors could easily contribute to elisions and conflations in classrooms where lessons on the entire sweep of black history are crammed into the shortest month of the year.

Meanwhile, the irony of a black man inventing the tool that helped turn slavery into the economic engine of the antebellum South is just too poignant to resist. As a Reddit commenter put it, “I always remember the story of Eli Whitney because it was kind of sad in a way, because this black man had inadvertently created a tool that encouraged people to have more slaves to operate these cotton gins and also influenced the power of cotton as an economic tool in the South.” That Whitney had trouble profiting from his patent—a true, if complex, part of his story—adds a plausibly bitter note: A black man invents a machine that oppresses his own people, yet he’s kept from benefiting financially himself? It sure sounds like America.

Kevin Webb, a 50-year-old adjunct history professor at Azusa Pacific University in California, has seen evidence for the belief in his own classroom. Several years ago, he said, a student in one of his survey-level U.S. history classes remarked on the irony of a black man inventing a machine that ended up promulgating slavery. Since then, he has asked his classes if they believe Whitney is black, and every semester there are numerous students who do. They insist they were taught this in elementary school. But Webb is among those wondering if the misconception is an example of the “Mandela effect,” a collective misremembering of specific facts. Examples include the existence of 1990s Sinbad movie Shazaam (never happened) or how to spell the “Berenstain Bears” (not -stein). The phenomenon is named for the widely shared certainty that Nelson Mandela died in jail in the 1980s. “No child ‘in my day’ was ever taught that Eli Whitney was black, but now they claim to be,” Webb told me by email. “Therefore this is either a more recent phenomenon, or it’s the Mandela Effect. Then certain students go on to become elementary teachers and then it becomes a fact, that indeed contemporary students were actually taught this misinformation.”

It’s almost like a sprawling, nationwide game of telephone. Speaking of which, did you know Alexander Graham Bell was black?

*Correction, Feb. 8, 2017: An earlier version of this post misstated the number of slave states in 1790. There were eight, not six.