His character and his role were already Western, he had only that way of asserting himself against the literary gentility with which her house was associated in his mind. (1.5.40)
A big reason why Susan falls in love with Oliver is that he's so quintessentially Western. He's like a hunky cowboy. Given that Susan spends most of her time hanging out with literary bigwigs and diehard intellectuals, meeting a rough-and-tumble dude like Oliver is like a breath of fresh air. It'd be like breaking up with a fashion designer to start dating a professional athlete.
She saw exotic red-barked trees among the woods, and smelled the herb-cupboard smells of sage and bay. Another world. (2.1.65)
Although she was scared at first, Susan actually falls in love with the West immediately. It certainly helps that it's super pretty out there, completely unlike the Northeast where she was born and raised. Like she says: it's another world.
"This is a place to be very happy in [...] but there is a thought [...] which is the undertone of our life here—that this is not our real home." (2.2.32)
Although she digs it out there, Susan is hesitant to call the West her home: she assumes that she and the fam will be heading back east in a few years' time. We're not trying to call her out or anything, but we're pretty sure that Oliver would disagree with that statement.
There are several dubious assumptions [...] that it was the home of intractable self-reliance [...] whereas in fact large parts of it were owned [...] by iron-fisted bosses. (2.5.50)
Looks like the Wild West wasn't so wild after all. This shouldn't be all that surprising; it's not like railroads pay for themselves. Still, it complicates our common stereotypes of the West, forcing us to reckon with the fact that this new country was built in large part through exploitative labor tactics.
Standing outside of this casual revelation of how deep and violent were the divisions in the camp, Susan felt as a woman [...] might feel if she [...] saw men fighting in the street. (2.7.103)
At first, Susan romanticizes the West. Although she doesn't think it's perfect or anything, she can't help but love how real things are out there. But then, she learns the truth. She learns about the harsh working conditions in the mines. She learns about the abusive labor practices employed by mine owners. She even learns about the awful violence that makes this economic revolution possible. It's a real eye-opener.
Oliver lashed it harshly with the whip [...] leaped to the ground and kept lashing [...] Susan sat white and trembling [...] hating the heartless mountains, the brutal West. (4.2.204)
Yikes—this is a side of Oliver that we've never seen before. But, it also seems like just another consequence of living out west: in order to survive in a brutal world, Oliver must become brutal, too. Yes, we know that this isn't exactly the sweetest thing to say, but it's an inescapable part of the life he's chosen.
Leadville roared toward civilization like a runaway train. Amid talk of an opera house, three mine managers [...] were planning houses on Ditch Walk. (4.4.61)
The times they are a-changing, huh? In only a few years, this tiny mining town has transformed itself into a mecca for wealthy Westerners. This just goes to show the massive economic impact that the then-burgeoning mining industry had on the western United States.
The West was not a new country being created, but an old one being reproduced; in that sense our pioneer women were always more realistic than our pioneer men. (4.7.15)
Interesting point, Lyman. In many ways, Susan is attempting to recreate the East Coast of her youth out west, shaping this wild country into something more familiar. That's a vastly different mindset from that of Oliver, who looks at the West and sees a blank canvas just waiting for him to jot down his masterpiece on it.
Mexico was indeed her Paris and her Rome [...] her only glimpse of the ancient and exotic civilizations that in her innocent nineteenth-century local-colorish way she craved to know. (5.1.26)
While most of the West is desolate and isolated, Mexico is a bustling hub of activity. What's more, it's an old country—quite the contrast from the West, where it's hard to find a building that's older than five years. While there are plenty of downsides to this traditionalism, Susan finds herself in awe of this mighty civilization.
Like everything here, it is large and raw. It is for the future, it sacrifices the present for what is to come. (8.3.3)
This is the West in a nutshell. For early pioneers, it wasn't about creating a better life for themselves—it was about creating a better life for those who came after. After all, there's little chance that their hard work would come to fruition in their lifetimes.