I have a copy from the University of California Press with a date of 
2002 but I fail to find an actual printing date.  The electronic edition 
found on the Mark Twain Project site gives dates of 2003, 2009, and 
2016.  I'm wondering if there are any substantive changes in these 
editions (printing runs?).  Actually, I'm trying to fix a date for Huck 
and Jim passing Cairo on their way down the Mississippi.  I've been 
poring over the history of Cairo for the past week and find written 
perceptions of this place to vary as much as the level of the 
Mississippi River, depending on the date observed.  From the Explanatory 
notes of my edition, Huck's passing Cairo would have been between 1835 
and 1845.  The year 1835 saw the beginning of the second, and ultimately 
failed, attempt to built a city on this dynamic piece of land at the 
confluence of the Ohio and Mississippi Rivers.

-- 
/Unaffiliated Geographer and Twain aficionado/