Michael,
    Try "The Ending of HUCKLEBERRY FINN: 'Freeing the Free Negro'" by
Charles H. Nilon in SATIRE OR EVASION (also published in the "Mark
Twain Journal" Vol. 22, Number 2, Fall, 1984.  Also see WRITING HUCK
FINN by Vic Doyno.  He theorizes that much of the ending was influenced
by Twain's interest in the abuses of the convict-lease system and
by the effects of international copyright laws on his finances.

KJB