If you’re more interested in the historical period than in “cowboy” stuff, you might like “Heart of the Country” by Greg Matthews. (It’s about a hunchbacked buffalo hunter, he sort of reminds me of Tyrion Lannister’s character in GRRMartin’s fantasy series.)
In addition to McMurtry’s Lonesome Dove series, try “Anything for Billy”, about Billy the Kid (naturally).
Another good one is “Tie My Bones to Her Back” by Robert F. Jones – I’ve read quite a few western/pioneer novels, and this is the first one that set out, in detail, what it was like to build a fire and cook a meal on the plains for a bunch of buffalo hunters.
The main character in “The Man Who Fell in Love With the Moon” by Tom Spanbauer is a half-breed bisexual boy who grows up in an Idaho whorehouse. He goes on a journey to discover the meaning of his Indian name. Mayhem ensues. It’s part comedy, mostly tragedy.
You might also like “Incident at Twenty Mile” by Trevanian. It’s a western-romance-psycho killer story set in a mining town. I adore Trevanian, he should publish more often.
“The Homesman” by Glendon Swarthout – a “homesman” is the guy who takes pioneer wives back east after they’ve lost their minds from prairie living, and dying.
Apologize for the long post, but I love this genre.
I like my westerns raw and gritty – no Laura Ingalls Wilder stuff here.