I picked up a copy a while ago and have played once. It's a twist on worker - I mean cowboy - placement. You are trying to get properties on a map grid and build various buildings for income. Starting map has a random seeding so it will never be the same game. Also has the possibility of dueling i.e. gunfight, the winner of which gets one of a better action or can place to steal half of a property's income...
It certainly could take an expansion.
Umm, do you have info on the expansion? This is the expansion forum.