Possible Duplicate:
How should I phrase a question that must be answered with an ordinal number (e.g., the third prime)?
How to ask a question to get a cardinal number answer
Neil Armstrong was the first man on the Moon.
I need to convert this into a question. If "Neil Armstrong" was the answer, the interrogative form would be
Who was the first man on the Moon?
How do you ask this as a question if "first" was the answer?
Another example would be
Abraham Lincoln was the 16th President of the United States