Conversation so far:
How many states is it in United States
In the United States, a state is a constituent political entity, of which there are currently 50.
what was the first US State
Delaware was the first state of the modern United States.
why is delaware considered the first state of the modern US
In Dover, Delaware, the U.S. Constitution is unanimously ratified by all 30 delegates to the Delaware Constitutional Convention, making Delaware the first state of the modern United States.

Question: which was the ninth state
Self-contained rewrite: which was the ninth state to ratify the constitution