Tough one. So much of what we think is 'authentic' frontier fiction was written long after the fact, full of romanticized myths. For a genuine feel, I keep coming back to novels that grapple with the sheer, grinding loneliness and the moral ambiguity of that expansion. 'My Ántonia' by Willa Cather captures that pioneer spirit, but it's the quiet, almost mournful nostalgia for a lost world that gets me. The land itself is a character, beautiful and brutal.
On the grittier side, Larry McMurtry's 'Lonesome Dove' might be the ultimate cattle-drive epic, but its authenticity comes from the flawed, tired men, not the mythic heroes. They're worn down by the miles. Cormac McCarthy's 'Blood Meridian' is the absolute antithesis of the romantic western—a terrifying, philosophical plunge into pure, nihilistic violence on the border. It feels less like a story and more like a biblical reckoning with the cost of that frontier madness. I can only read it every few years; it leaves a mark.