After gold was discovered near Bannack, Montana, in 1862, prospectors scoured every gully and creek searching for the next bonanza. In 1863, Walter Washington DeLacy led a 40-man expedition that explored the Snake River to its source. The party didn’t find enough “color” for a paying proposition, but they did bring back a wealth of information about the Yellowstone Plateau. DeLacy included that information in his famous 1865 map of the Montana territory.