The End of the Trail by Brett Halliday

When two prize cattle are slain, the sheriff of Powder Valley is called to a freezing, violent town

It’s bitterly cold in the Rockies when the locomotive reaches the end of the line. Only one passenger alights from the caboose: Nate Morris, a lean private detective with an easy grin and icy eyes. Sanctuary Flat is a grim little town, alone in the mountains and cut off from the world. The only business there is cattle breeding, and business is rotten. Two prize cattle have been killed, and the owners have hired Morris to find out what happened.
 
When Morris is found with a knife in his throat, the men who run Sanctuary Flat call on the only men tough enough to tame this wild ranching town. Pat Stevens, sheriff of Powder Valley, and his sidekicks, Sam and Ezra, have faced death dozens of times. But nothing can prepare them for the evil corruption at the heart of Sanctuary Flat.