I'm in my mid-50s, maybe you are older than me. It's something I had heard about in the 2015-2020 timeframe. I'm white as fuck, but being online meant I saw tweet threads or short explainers about it for a few years. I didn't meet folks who celebrated it, but when I asked around to Black folks I knew they were like, "Yeah, it's a thing."
So I suspect that the holiday gained momentum among Black Americans and spread out from Texas sometime prior to me hearing about it, perhaps with the rise of social media, and then us folks who are out of the loop started hearing about it later. (Either through our own social media intake or through the declaration of a federal holiday.)
> This holiday is beyond stupid when you consider that the guy who freed the slaves, Abraham Lincoln, doesn't have a Federal holiday where one gets the day off.
Don't see why we can't have both.