Zane Grey 
The Rustlers of Pecos County [EPUB ebook] 

Texas. They took the most contrary bunch of frontiersmen, ranchers, farmers, cowpokes, shiftless no-accounts, shootists rascals, and politicians, jumbled them together, and somehow formed a state. They called it Texas, but for defenseless women and children, it was hell.
Texas Rangers. Although they were outnumbered a thousand to one, the Texas Rangers fought a holding action against the complete breakdown of law and order, often paying for peace with their lives. But one county held out against attack after attack, a place so mean that a saint would have turned bad.
Into this valley of death rode Ranger Vaughn Steel, hungering for revenge, thirsting for justice, and determined to wipe out the rustlers of Pecos County…