The wikipedia page X rating X rating - Wikipedia lists The Evil Dead as one of main stream films that received an X rating but the wikipedia page for The Evil Dead doesn’t state it was X-rated.
I saw The Evil Dead in the theatre during its first run. I was 12. My hometown theatre owner didn’t enforce restrictions on R rated movies. He just cared about the money for your ticket. But X rating? I doubt an X-rated film would even be shown at all in my Kansas home town. I’m sure if it had been rated X I would have known and remembered it.
Originally rated “X” for gore, etc., re-rated “NC-17” in 1994 after that rating became available (and no one wanted an “X” rating for a non-porn film anymore).
X doesn’t (or at least, didn’t originally) mean that a movie was porn. Originally, it just meant that the filmmaker hadn’t bothered to submit it to the ratings board. The board could assign an X, and would if someone actually submitted a porn film to them, but why bother if you know it’s going to be X anyway?
It’s not that rare. I’m not saying no theater ever of those days kept underage kids out, but it was certainly not hard to get into such movies back then. It wasn’t really until Showgirls came out that there started to be a big push to actually make sure things were enforced by the theaters. Mainly out of fear of bad press, mind you, since MPAA ratings carry no legal authority.
Anyone could use X for anything they wanted, as the MPAA declined to trademark the X rating, unlike the others. That’s probably the main reason they later brought in the NC-17 rating, so they could have something trademarked and not have to be associated with all the pornographers throwing “their” rating around.