You may notice that most 529 plans reference a specific state either on their plan website or in their plan name. 529 Plans are sponsored by states, and many states even offer multiple plans to choose from.
It is important to note that an individual wishing to open a 529 is not required to participate in an account offered by the state they reside in. You may have the opportunity to open an account with a 529 plan offered by a different state. Plan program descriptions (commonly listed on plan websites) may be referenced to determine eligibility requirements.