The location cited is probably the town of Chester.  

Jackass Hill takes its name from mules that clustered around it when it was a pack-train stop.  It became a placer-mining boom town in 1848.  "By the time Clemens arrived there in early December 1864, the camp was a pale shadow of its former glory."  Clemens spend almost three months there with Dick Stoker, Jim and William Gillis, and their cat Tom Quartz.

This site is probably located one and one-half miles southeast of Ovid, in Sedgwick County, Colorado. Sources generally agree on the location of the Julesburg Station site and its identity as a Pony Express and stage station. On the L. & P.P. Express Co. station list, it was probably called Upper Crossing, South Platte or Morrell's Crossing. In 1859, Jules Reni established a trading post at the site and served as station keeper for the Pike's Peak stage line and the Pony Express.

The term Great American Desert was used in the 19th century to describe the western part of the Great Plains east of the Rocky Mountains in North America to about the 100th meridian. It can be traced to the 1820 Stephen H. Long's scientific expedition which put the Great American Desert on the map.

Founded in 1859 after a gold strike was made south of Mount Davidson.  It became one of Comstock's most prosperous towns while Twain was in Virginia City with a population of about 3,000 people.  By the 1870s, more than 10,000 people lived there, merging with Virginia City.  The area soon declined and is now little more than a ghost town.