Do I need a registered agent in every state?

The registered agent requirement follows the entity's registration, not the owner. Your formation state expects an agent, and every additional state where you complete Foreign qualification expects one too, each with a real street address inside that state. There is no national agent that covers you everywhere at once, because each state maintains its own records and its own Service of process rules.

For a company in two or three states this is manageable, but the coordination gets harder as the footprint grows. Different renewal cycles, address changes, and forwarding rules multiply with each state. A multi-state registered agent service consolidates the appointments so notices and deadlines are tracked in one place rather than scattered across state records.