The new numbering plan divided the North American continent into regional service areas, called numbering plan areas (NPAs), primarily following the jurisdictional boundaries of U.S. states and Canadian provinces. States or provinces could be divided into multiple areas. NPAs were created in accordance with principles deemed to maximize customer understanding and minimize dialing effort while reducing plant cost. Each NPA was identified by a unique three-digit code number, that was prefixed to the local telephone number. If a call's destination was within the same numbering plan area, dialing the area code was not necessary.