Relief methods
Area Code Splits
Before overlays took over, the way to add numbers was to split a region in two. Some people kept the old code; others got a new one.
Last updated June 5, 2026
A split divides a single area code's territory into two or more parts and assigns a new code to one part. Unlike an overlay, a split forces some customers to change their area code. Splits were common through the 1990s but are rare today because overlays avoid the disruption.
How a split works
In a split, regulators draw a new boundary through an existing area code's region. One side keeps the original code; the other side is reassigned to a brand-new one. For decades this was the default way to relieve an exhausted code. The downside is obvious: half the region wakes up with a different area code and has to update everything from business cards to alarm systems.
Split vs. overlay
The key difference is who has to change. A overlay changes nobody's number but requires 10-digit dialing for all. A split changes the area code for a large group of people but can preserve seven-digit local dialing on each side. Because consumer and business groups strongly prefer keeping their numbers, regulators have favored overlays almost exclusively since the early 2000s.
Famous historic splits
California's 213 originally blanketed all of Southern California before a cascade of splits carved out 310, 818, and others. New York's 718 was split off from 212 in 1984 to cover the outer boroughs. These boundary changes shaped the map you see today.
Will my area code ever be split?
It's very unlikely now. Modern relief is done with overlays, so the realistic change you'll experience is a new code appearing alongside yours, not your number being reassigned. Track upcoming relief on the newest area codes page.
Quick answers
Frequently asked questions
What is the difference between a split and an overlay?
A split reassigns part of a region to a new area code, so some people's numbers change. An overlay adds a new code over the whole region, so nobody's number changes but everyone dials 10 digits.
Do splits still happen?
Rarely. Since the early 2000s nearly all area code relief has used overlays because they avoid forcing customers to change their numbers.
Did a split ever change someone's phone number?
Yes — the area code portion. In a split, customers on the new-code side of the boundary received a different 3-digit area code while keeping their 7-digit local number.
Keep reading
Related guides
How US Area Codes Work · Overlay Area Codes Explained · 10-Digit Dialing · Toll-Free Numbers · Newest & Upcoming Area Codes · Retired & Changed Area Codes · Spam & Scam-Risk Area Codes · Area Codes Near Me