So there was a time period in the Americas — the US — where there was a major expansion of colonization, pushing west. We landed on the East coasts and stayed there, but then decided to IDK take over everything because that's what white people did. So this is a time period when the western part of the US was not quite as "tamed." Laws were a little different, lots of horses and cowboys.
TBH, it wasn't my favorite time period. There were a lot of "skirmishes" with native tribes that were being pushed off their land, but people have romanticized it in movies.