"American Horror Story﻿" fans are going to get a dose of seriously creepy history in season 6 ... at least based on these pics we got from the set.

TMZ has obtained the first shots from the 'AHS' set in Santa Clarita, CA ... and one word etched into a tree is a HUGE hint about the theme: CROATOAN.

If you paid attention in school ... you remember that word from the mystery of Roanoke -- the 1590 North Carolina colony where 117 people vanished. The only clue was the word "CROATOAN" -- a nearby Native tribe -- carved into bark. There have been all kinds of creepy legends about the colony.

Check out the set pics -- they all center around a colonial-era farm. Plus, our 'AHS' spies have spotted the cast in Pilgrim-era clothing, and the the teaser trailers are on point, too.