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 consistency, answers should be in all lower cased letters.
PROBLEM: Category: FUN ACROSS AMERICA 
Clue: Wild West fun abounds during Cheyenne Frontier Days in this state

SOLUTION: wyoming

PROBLEM: Category: THE 1930s 
Clue: On September 18, 1934 the Soviet Union joined this international organization

SOLUTION: league of nations

PROBLEM: Category: DISCOVERIES 
Clue: By Rutherford in 1919, this particle, 22 years after the electron

SOLUTION:
the proton