I stumbled across this article about a steam-powered prairie hauler in the Denver Weekly Commonwealth of July 16, 1863 (p. 1). Steam-powered transport was an old idea by this time, even in the US. Steam-powered trains had been running in the US since about 1830; steam-powered ships and boats were crossing the oceans and blasting each other out of the water in the War of the Rebellion. Even steam-powered land vehicles had been built and used, perhaps as early as the 1600s but more famously by Cugnot in the 1700s. Such vehicles apparently existed in significant enough numbers in England in the early 1860s to prompt reactionary legislation. The Red Flag Law restricted speeds to 4 miles-per-hour and required any 'road locomotive' to be preceeded by someone waving a red flag. Later on, during the first decade or so of the automobile age, external combustion engines competed with gasoline and electric engines for supremacy, and tended to fare well. This article, however, is one of the earliest references I've ever seen to a steam-powered road vehicle in the United States. And it's the only reference I've seen to steam power on the wagon roads of the plains.

The reasons why the venture failed I think are contained within the article. First of all, the vehicle consumes its wagon-load of wood and water relatively quickly, then it needs a reload. Since there literally isn't a tree between Nebraska and Denver at this time it's fair to ask, reload with what? It would take an entire separate logging-and-hauling enterprise just to keep the vehicle rolling. Railroad locomotives also required a good deal of logistical back-up, but this thing, which apparently needed a costly road of its own in any case, couldn't haul nearly as much as its rail-bound cousins. So that's a deal-breaker, ladies.

The railroad would reach over to Denver in 1868.