Wei Miller

Description of USA Phone Numbers

USA telephone numbers adhere to the North American Numbering Plan (NANP) also encompassing Canada, some islands of the Caribbean, and US possessions. Here is a full description:

Structure & Components
Country Code: +1 (shared by NANP countries).
Area Code: 3 digits, starting with 2–9 (e.g., New York is 212, Los Angeles is 310). Originally geographic, now typically overlayed owing to use.
Local Number: 7 digits, broken into a 3-digit central office code (exchange) and 4-digit subscriber number.

Full Format:
International: +1 (XXX) XXX-XXXX
Domestic: (XXX) XXX-XXXX or 1-XXX-XXX-XXXX (for long distance).

Key Features
10-Digit Dialing: Required in most regions, even for local calls.
Toll-Free Numbers: Prefixes 800, 888, 877, 866, 855, 844, 833 (e.g., 1-800-FLOWERS).
Emergency Services: Dial 911 throughout the nation. Non-emergency numbers (e.g., 311, 411) are location-dependent.
Premium Services: Prefixes such as 900 are billed extra.

Formatting Styles
Domestic: (555) 123-4567 or 555-123-4567.
International: +1 555-123-4567 or +15551234567 (no separators).

Geographic vs. Portability
Area Codes: Formerly used areas, but mobile numbers and number portability allow retention of numbers across location.
Mobile/Landline: Numbers are not differentiated by digits; service type is identified by carrier.

International Dialing
Calling the US: Call [International Access Code] +1 XXX XXX XXXX (for example, 00 +1. in Europe).
From the US: Call 011 + [Country Code] + [Number].

Considerations
Spoofs: Spoofed area codes are the norm; verify calls from strangers.
Vanity Numbers: Use phone keypad characters to spell out numbers (1-800-CONTACT).

Samples
National: (212) 555-0199
International: +1 800 555 0199
Toll-Free: 1-888-123-4567

U.S. phone numbers balance geographic convention and modern versatility to meet mobility and technological change and maintain a uniting pattern.