It all comes full circle to the Mormons, dun't it? In Roughing It, Twain travels through Mormon Territory and documents polyg SLC. Fascinating stuff.
"Documents" is not quite the right term. "Mocks mercilessly" is a better term, especially for the section detailing the effects of a single child in a Mormon household getting a tin whistle from a stranger, and all the kid's half siblings demanding one as well.
The section on Valley Tan is interesting as well.