The North American Numbering Plan (1947)

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As direct dialing became more prevalent, there was a need for a standardized system that could handle long-distance and cross-country communication.

Creation of the NANP
In 1947, AT&T introduced the North American Numbering Plan (NANP) to bring uniformity across the United States, Canada, and parts of the Caribbean. The system introduced a 10-digit numbering structure:

3-digit Area Code (NPA - Numbering Plan Area)

3-digit Central Office Code (NXX)

4-digit Line Number

Example: (212) 555-1234

This structure enabled Direct Distance Dialing (DDD), allowing users to place long-distance calls without operator assistance. Area saudi arabia phone number data also helped categorize regions based on population density and telephone infrastructure.

International Standardization
As telephone networks expanded globally, different countries developed their own numbering systems. However, the lack of international standardization posed challenges for cross-border communication.

ITU and E.164 Standard
To solve this, the International Telecommunication Union (ITU) introduced the E.164 numbering plan — a globally accepted standard for public telecommunication numbering.

E.164 defined the format for international telephone numbers:

Maximum length: 15 digits

Format: [Country Code][National Number]

Examples:

+1 212 555 1234 (USA)

+44 20 7946 0958 (UK)

+91 22 1234 5678 (India)

This system became the backbone of international dialing and continues to be used today.