"As a wealthy upper-class young man enters adulthood during the second US civil war, he is suddenly disowned and ousted from his family estate, causing him to experience the life of the impoverished in a military-industrial society, eventually joining the ranks on the front line to prove to his father he deserves his inheritance."

Thanks for the feedback, I have a new logline up!

Definitely way too long, with too much description not adding up to anything. Wealthy and upper class mean the same thing; no need for both. Same deal with disowned and ousted from family: exact same meaning. Why was he disowned, anyway? Just because? You have to provide more detail than this. We have to know who's doing what and why. And how does joining the ranks prove something to his father? What does he even need to prove? We need the biggest plot points, the main protagonist and antagonist, the major motivations. And that's about it.

Was there a second US civil war? I thought there was only one in the late nineteenth century.

This logline uses too many words to describe too few plot elements "... upper-class young man?" is a vague description if his flaw is being spoiled or immature then say so. Upper-class can be interpreted in many ways and young man means nothing in a logline as it doesn't describe enough.

The inching incident should be one event either being disowned or ousted as one is implicit of the other. Secondly let the main character be an active one not passive, the inciting incident shouldn't cause him to experience something, rather it should motivate him to do something.

Lastly if his goal is money then he is not a particularly nobel character why not make your hero just that a hero. Let his goal be something greater than him this way he will prove that he has learned his lesson and is no longer a spoilt rich boy that cares only for him self.

e.g:
After his father disowns him a spoiled brat must join the army to survive the US civil war and lead his platoon to victory in order to save his home town.

Not sure this is the story but the elements are in the line.

Hope this helps.