If you've been playing 'Red Dead Redemption 2' over the weekend, you'll no doubt have noticed a significant amount of Irish characters in the game.

The game starts off with Arthur Morgan in a pitched battle with the O'Driscolls, a fictitious gang led by a man named Colm, an Irish immigrant who has a blood feud with Dutch. Shortly thereafter, you're sent out to find Sean Macguire, a member of the Van der Linde gang who's been captured by bounty hunters. In fact, throughout the game, you regularly encounter Irish NPCs (non-player characters) and enemies.

Why so?

Well, between 1820 and 1860, Irish people constituted at least a third of all immigrants into the US. From 1820 to 1930, it's estimated that 4.5 million Irish people moved to the US, many of them fleeing the Great Hunger, colonial persecution, or trying to begin a new life.

While a significant portion of immigrants stayed on the east coast, settling in urban centers such as New York and Boston, there were some who left the slums and travelled west to either settle or take up work in mining and farming.

Of course, out of this number, there were some who began criminal careers in America. One of the most well-known outlaws of the West, who died approximately ten years before 1899 when 'Red Dead Redemption II' is set, was Billy the Kid.

Born Henry McCarty, Billy the Kid's parents were Irish immigrants Catherine (nee Devine) and Patrick McCarty. Though the precise whereabouts of his mother's birthplace in Ireland isn't known, Billy the Kid would for a time go by the name Kid Antrim. Billy the Kid was shot in 1881 by lawman Pat Garrett, who himself was the grandson of Irish immigrants.

Another man shot by Garrett and was considered Billy the Kid's best friend was Tom O'Folliard, who was born to Irish immigrant parents in 1858 and died in 1880. Both he and Billy the Kid were Regulators - a deputised posse of gunfighters who fought in the Lincoln County War, and later became a loose band of cattle thieves.

The likely inspiration for the O'Driscolls, the main protagonists of 'Red Dead Redemption II', came from the Daly Gang. Led by John Daly and 'Three-Fingered' Jack McDowell, the Daly Gang were known for violent robberies and took part in a 25-year reign of terror across Nevada. One of its most prominent members was 'Irish' Tom Carberry, who was one of the few survivors of the gang.  Not much is known about Carberry's early life, but it is known that he was a famed gunfighter and regularly took part in duels in Aurora, Nevada.

It wasn't just all outlaws, however.

William 'Buckey' O'Neill, who was a sheriff of Yavapai County in Arizona and would later take part in the Spanish-American War of 1889, was born to Irish parents. O'Neill was also known for his membership of the Rough Riders, a cavalry group led by Theodore Roosevelt - who'd go on to become the 26th President of the United States.

While it might seem a bit strange for Irish people to hear so many similar voices throughout a videogame, it's actually historically accurate for the time period 'Red Dead Redemption II' is set in.