The 1600s
There is a theory that claims blackjack was invented by the Romans. It has never been proven, and seems to be based entirely on the fact that the Romans liked to gamble.
The first recorded mention of a blackjack-like-game appeared in the short story, ‘Rinconete y Cortadillo’, by Miguel De Cervantes. Named ‘veintiuna,’ the object of the game is to reach 21 points without going over, with the ace being valued at either 1 or 21.