Unlike some of our more modern casino games, Blackjack has a long and varied history which definitely dates back around 400 years and possibly as far back as ancient Chinese gamblers - although it's always easy to pin this type of thing on the Chinese without much evidence. Our 400 year date is thanks to a collection of short stories by Miguel de Cervantes, the author of the more well known Don Quixote who, in 1613, published the set of writings under the title Novelas Ejemplares.
The particular novellete which interests us is called Rinconete y Cortadillo, the protagonists being two ne'er do wells in contemporary Spain who pay their way by cheating in various card games. One of these card games of course bears an uncanny resemblance to Blackjack - in fact it's even called Ventiuna, 21 in Spanish and not too far removed from the French term Vingt et Un.

The game was described in some detail in Cervantes story and from those details we can discern that the similarities between Ventiuna and modern day Blackjack are too numerous to be a coincidence. For example the objective is to get a two card total of 21 or under; additionally Aces are worth either one or eleven. Where the game does differ is that Spanish Baraja decks of cards do not use eights, nines or tens.
A game of this simplicity travelled well and it was soon played in various European countries. The next obvious destination was the Americas as waves of European immigrants arrived in subsequent years. The name Blackjack is in fact American in origin - to give it a boost in its early days a bonus was available if the player was holding the Ace of Spades and a black Jack (of either suit). The bonus disappeared but the name remained and Blackjack is still the most popular banking card game in the world.
For a bit of perspective, Blackjack's 400 year old age compares to around 200 years for early versions of Five and Seven Card Stud and a mere 100 or so years for the youthful Texas Hold'em.