The place is Virginia City, and the source is, more or less, "Roughing It,"
chapter XLIII.  I say "more or less" because the version you're quoting is
actually from Hal Holbrook's "Mark Twain Tonight" (Twain's version doesn't
include the part about being a Presbyterian).  Here's the paragraph from
"Roughing It":

Virginia had grown to be the "livest" town, for its age and population, that
America had ever produced. The sidewalks swarmed with people -- to such an
extent, indeed, that it was generally no easy matter to stem the human tide.
The streets themselves were just as crowded with quartz wagons, freight
teams and other vehicles. The procession was
endless. So great was the pack, that buggies frequently had to wait half an
hour for an opportunity to cross the principal street. Joy sat on every
countenance, and there was a glad, almost fierce, intensity in every eye,
that told of the money-getting schemes that were seething in every brain and
the high hope that held sway in every heart. Money
was as plenty as dust; every individual considered himself wealthy, and a
melancholy countenance was nowhere to be seen. There were military
companies, fire companies, brass bands, banks, hotels, theatres,
"hurdy-gurdy houses," wide-open gambling palaces, political pow-wows, civic
processions, street fights, murders, inquests, riots, a whiskey mill
every fifteen steps, a Board of Aldermen, a Mayor, a City Surveyor, a City
Engineer, a Chief of the Fire Department, with First, Second and Third
Assistants, a Chief of Police, City Marshal and a large police force, two
Boards of Mining Brokers, a dozen breweries and half a dozen jails and
station-houses in full operation, and some talk of building
a church. The "flush times" were in magnificent flower! Large fire-proof
brick buildings were going up in the principal streets, and the wooden
suburbs were spreading out in all directions. Town lots soared up to prices
that were amazing.

Jim Leonard