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.

Category: "N" JOY 
Clue: A songbird, or the last name of nursing pioneer Florence
nightingale

Category: THE U.S. CONGRESS 
Clue: Frustrated with his own political party, in 2001 this senator from Vermont switched to indepedent
jeffords

Category: NATIONAL HISTORIC SITES 
Clue: The Greenville, Tennessee historic site honoring this president preserves his 2 homes, tailor shop & gravesite

andrew johnson