What is the oldest state in the United States?

Florida has the oldest settlement in the United States with St. Augustine. The Spaniards settled here in 1565.

Virginia was the first of the original thirteen colonies and was started by the settlement of Jamestown in 1607.

Delaware was the first state and was created in 1787. With due respect to the answer of Florida and Virginia, Delaware was the first former colony that ratified the US Constitution, and thus became the first US State.
As Delaware was first to ratify the US Constitution it became the oldest State in the United States. This is the only correct answer to the question.