What if Twain had been born a century later - same place, but in 1935? Early boyhood memories would have been of WWII, and he would still have been relatively young and I assume of draft age during the Vietnam War. Would he have dressed like Jimi Hendrix and gone to Woodstock? What would he have written about Watergate? 
What about Space travel? Would he have been an early adopter of computers, social media, etc.?

Perhaps he would have invested in Apple from the outset and been too distracted with business matters to write much...
If his life span remained the same, he would have died about the time Obama took office.
Of course, it's impossible to know the answers to these things for sure, but a Twainian with a talent for alternative history fiction might be able to come up with some plausible and interesting scenarios. - B. Clay Shannon