system
Given the following post, respond as if you're commenting on Reddit:
human
[Fallout New Vegas] What did the NCR run into at Big Mt.?

When speaking to Joshua Graham about the NCR's supply routes, he mentions how Big Mt. was a major obstacle, because it "might as well be a wall to men". What did he mean by that? Did the radar fence keep people out, or was it all the lobotomites and rogue TOHs? I don't recall anything keeping The Courier from leaving except his tesla coils.
gpt
It's a shit place to run caravans through, for several reasons. 

1) Shit terrain: the area around it is more mountainous than most parts of Zion or lower Nevada. Hard to get Brahmin up the side of a cliff with gear on their back.

2) things that go bump in the night: Lobotomites and the tRoboscorpions tend to eat whatever shows up. No caravan gets through alive. 

3) lack of resources in the area: The Big MT is...pretty empty. The area was made by blowing the top off a mountain and thus has little plant life or surface water. Not much to scavenge.

So there you have it. Bad land, bad inhabitants, bad resources.