What are the themes, and how do the these reflect the social issues of the late 1800s? Is the story written in response to a social issue?

One of the themes in this story is Illusion vs. Reality--things are not always what they seem to be.  This theme absolutely reflects the social issues of the mid to late 1800's since the Gold Rush and The Civil War were not a romantic and glorious as some expected them to be.  Not everyone ended up grotesquely wealthy who chased the "get rich quick" element of the Gold Rush.  Many ended up destitute, and many others even lost their lives due to greed and violence erupting from claim issues. 

The Civil War was just as glorified with flocks of people riding out in the carriages to be spectators much like they would a play or a movie today.  Illnesses, camps for captives, and hospitals proved to be any but glorious and romantic.

Another theme is that of gambling and taking fate or chance by the horns.  Gamblers have nerves of steal, and in this story the gamblers have their run of bad luck streaks.  Along the same lines, anyone who opted to jump on the bandwagon of the Gold Rush were taking huge chance--if their luck was good, great!  However, it was just as often bad luck...not just with not finding gold, but losing money, and sometimes their lives.