TASK DEFINITION: You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.
PROBLEM: Category: PUBLISHING FIRSTS 
Clue: In 1908 Ernest Henry Shackleton printed the first book on this continent

SOLUTION: antarctica

PROBLEM: Category: CIVIL WAR SITES 
Clue: Of the 6 Civil War-related national military parks, the northernmost & southernmost are in these 2 states

SOLUTION: pennsylvania & mississippi

PROBLEM: Category: THE '90s 
Clue: In 1998 Andrew Thomas became the seventh & last American to live aboard this

SOLUTION:
space station mir