Area Code Family Trees
Since 1947, 79 root US area codes (including 77 assigned in the original NANP and 2 later independent assignments) have spawned 296 descendants through splits and overlays. Explore the family trees to see how area codes relate to each other.
Largest Family Trees
Area Code 305
FL • 22 descendants
Area Code 213
CA • 21 descendants
Area Code 415
CA • 14 descendants
Area Code 404
GA • 10 descendants
Area Code 704
NC • 10 descendants
Area Code 201
NJ • 9 descendants
Area Code 703
VA • 9 descendants
Area Code 312
IL • 8 descendants
Area Code 212
NY • 7 descendants
Area Code 617
MA • 7 descendants
Interactive Family Tree Visualization
Scroll to zoom • Drag to pan • Click a node to view its area code page
Quick view — select a tree:
Key Findings
- The deepest family tree descends 4 generations from its root — area codes have been split and overlaid up to 4 times from their original 1947 assignment.
- The three largest family trees belong to 305 (FL), 213 (CA) and 415 (CA).
- Since 2000, most new area codes have been overlays rather than splits, preserving existing numbers while adding capacity.
All Root Area Codes
These 79 area codes have no parent in the family tree — 77 were assigned in 1947 as part of the original NANP, and 2 were independent assignments created in 1957. Click any code to see its full family tree.
Understanding Area Code Family Trees
Area code family trees show the genealogy of telephone number planning areas. The 77 original area codes assigned in 1947, plus 2 later independent assignments, form the 79 root families. They have grown to 375 tracked codes — 296 of them created through splits and overlays, 372 currently in service, and 3 assigned but not yet in service.
Splits vs Overlays
A split divides an existing area code's territory, assigning part to a new code. An overlay adds a new code over the same territory, requiring 10-digit dialing. Most codes since 2000 are overlays.
How to Read the Trees
Each box represents an area code. Lines show parent-child relationships. The root (original) code is at the top, with descendants branching below. Click any code to see its full details and local calling area.
Why 79 Root Codes, Not 77?
This page lists 79 root codes — all area codes with no parent in the family tree. This includes 77 codes assigned in 1947 (the original NANP) plus 2 independent codes created in 1957 that were not derived from any existing code. The Statistics page shows77 "Assigned in 1947" because it counts only codes with an in-service date within 1947 itself. Both numbers are correct — they use different definitions of "original."