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: BASEBALL 
Clue: Say hey! This Giants centerfielder appeared in a record-tying 24 All-Star games
willie mays

Category: BUSINESS & INDUSTRY 
Clue: This stagecoach company owned the Pony Express during the last few months of its existence
wells fargo

Category: THE HISTORY OF APRIL 9th 
Clue: 1959: NASA publicly introduces Messrs. Glenn, Shepard & the rest of this program's 7 astronauts

mercury