This book began with a ride on the historic Durango & Silverton Narrow Gauge Railroad, the famous scenic train route through the San Juan Mountains of Southwestern Colorado. I was on a book tour and headed to the old mining camp of Silverton, high in those mountains, to give a talk about John Henry “Doc” Holliday, who had spent some time gambling there according to a report in an 1885 newspaper. The route was beautiful, the narrow rails clinging to the cliff walls with spectacular views of the Animas River far below—a sight that Doc Holliday had surely also enjoyed on his way to Silverton. And somewhere along the way, I realized that no historian had yet written about Doc’s travel routes—and that most of those travels went by rail, as for most of his life he went where the railroads went or where they were coming and bringing business. He was not a frontiersman, living off the land. He was not a Southern planter living off the labor of slaves who worked the land, although that had been his legacy. He was a modern Victorian man, well-educated and well-trained for a professional career, a man whose life seemed destined to be lived in the cities of nineteenth century America, cities connected by thousands of miles of rail. If his circumstances hadn’t taken a surprising change, sending him West into legend as Doc Holliday, he would likely never have taken part in a posse ride across a Western desert, or taken a stage coach ride across a precipitous Rocky Mountain pass. But even in the West, most of his journeys were made by rail and most of his sightseeing was done from the windows of a railcar.