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.
Input: Category: REMEMBERING U.S. HISTORY 
Clue: Issued in 2011, a stamp commemorating the 150th anniversary of a major event in U.S. history depicts this stronghold
Output:
fort sumter