Virgin River (Skye's West Series #16) by Richard S. Wheeler
This is the sixteenth novel in Richard S. Wheeler's long-running series about Barnaby Skye, the British seaman who carves out an amazing life for himself in the North American Wilderness, along with his wives and his ugly, cantankerous horse, Jawbone.
In Virgin River, the famed mountain man and his two wives, Victoria of the Crows and Mary of the Shoshones, take a party of tubercular young people to the southwestern desert where they hope to be healed. Their destination is the Virgin River, where the mild, dry climate offers a cure. This time, Skye and his wives must cope with rival guides and cross Utah at the time of heightened tensions between the federal government and the Latter-Day Saints.
Skye soon discovers that other wagon companies on the trail fear the sick and blame them for every ill that overtakes their own companies. Taking a party of sick people along the California trail requires every bit of skill and courage that Skye and his wives can muster. And hovering over the trip is the looming catastrophe of war.