This is called a "map legend" or a "map key". It's usually located on the side or on the bottom, whether some space is available and it lists the symbols used in the map along with their meaning.
This is a non-binding, collaborative arrangement among its members that provides a legal framework for states to assist one another in managing a disaster or an emergency that has been declared by the government of the impacted state. This mutual aid agreement is EMAC or Emergency Management Assistance Compact.
The power was mainly given to State Governments.
