Area Code Guides
In-depth reference articles about North American area codes — history, geography, how splits and overlays work, and more.
Puerto Rico and the US Virgin Islands: Area Codes of US Territories
Puerto Rico and the US Virgin Islands are US territories with their own dedicated area codes. Here's what you need to know about calling 787, 939, and 340.
555: Why Hollywood Uses Fake Phone Numbers
Every movie and TV show uses 555 numbers to avoid accidentally broadcasting real people's phone numbers. The story behind this convention is more interesting than you might think.
Area Code 303: Colorado's Original Number and Denver's Growth
Area code 303 has been Colorado's defining number since 1947. As Denver has grown into a major metro, the original code has been supplemented but never replaced.
Area Code 305: Miami and the Story of South Florida
Area code 305 is one of the most culturally significant numbers in America. It's synonymous with Miami, but it once covered all of Florida. Here's its full history.
Why Texas Has More Area Codes Than Any Other State
Texas is home to more active area codes than any other US state. Its combination of enormous size, fast-growing cities, and booming economy tells the whole story.
Area Code 617: Boston, New England, and the Story of the Hub's Number
Area code 617 has served Boston since 1947, but it once covered all of New England. Here's how Massachusetts got its current area code geography.
Mountain Time Zone Area Codes: The Interior West
The Mountain Time Zone covers the Rocky Mountain states, the high desert, and the Canadian prairies. Here's a guide to the area codes of this vast interior region.
Pacific Time Zone Area Codes: From Seattle to San Diego
The Pacific Time Zone runs down the entire West Coast of the US and Canada. Here's a complete overview of the area codes in California, Oregon, Washington, and British Columbia.
Central Time Zone Area Codes: The American Heartland
The Central Time Zone stretches from the Canadian prairies to the Gulf of Mexico. Here's a guide to the area codes of this vast mid-continental zone.
The Chicago Split: How 312 Became 773, 708, 847, and More
Chicago started with a single area code in 1947. The city's growth forced repeated splits that turned one code into six. Here's the story of 312 and its successors.
Caribbean Area Codes: The Islands of NANPA
Nineteen Caribbean nations and territories are part of the North American Numbering Plan. Calls to Jamaica, Barbados, and the Cayman Islands use +1 — but they're not domestic.
Eastern Time Zone Area Codes: A Complete Guide
The Eastern Time Zone is home to more area codes than any other in North America. Here's a comprehensive guide to every state and territory in the Eastern zone and their codes.