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: U.S. TRANSPORTATION 
Clue: Writing in the 1820s, Lafayette's secretary called it a "great channel of communication, executed in eight years"
Output:
the erie canal