Key Findings
CA's 213 spans 4 generations from root to deepest descendant — the largest US family by full lineage
213 descends 4 generations from root to deepest descendant (splits and overlays combined)
20% of all root codes have never been split or overlaid
The 213 area code (CA) is the most complex family tree in the US (complexity score 80) — and also the largest, with 22 total codes spanning 4 generations of splits and overlays. Its longest split chain (213 → 714 → 619 → 760) chains 4 codes — a pattern driven by successive splits, each added as number demand in the region grew. In contrast, 20 root codes remain completely solo, never having spawned a single descendant.
Family Size Distribution
Most area code families are small — but a handful of mega-families dominate the landscape.
The distribution is heavily right-skewed: 20 families (20%) have just one code, while the top 3 families account for 41 codes (11.0% of all area codes).
Depth & Split Chains
Some area codes went through multiple generations of geographic splitting before reaching their current form. These chains reveal the layered history of US telecommunications growth.
Longest Split Chains
The 213 → 714 → 619 → 760 chain (4 levels) is the deepest split chain in the US. Each arrow represents a geographic split where a new area code was carved from an existing one.
Overlay Complexity
Overlay codes don't split geography — they add a new code on top of an existing area. Families with many overlays face a different kind of complexity: multiple codes sharing the same footprint.
Overlays equal or outnumber splits — indicating number exhaustion rather than geographic carving
214 — 3 overlays out of 5 descendants
All Families
Browse all 100 root families ranked by complexity score. Click any root code to view its detail page.
How Complexity Is Calculated
The complexity score (0–100) is a weighted composite of three dimensions:
The highest-scoring family (213, CA) reaches 80. Each dimension is normalized to its observed maximum, then weighted and summed.
| Root↕ | State↕ | Codes↕ | Depth↕ | Overlays↕ | Splits↕ | Groups↕ | Complexity▼ |
|---|---|---|---|---|---|---|---|
| 213 | CA | 22 | 4 | 1 | 20 | 1 | 80 |
| 212 | NY | 8 | 3 | 3 | 4 | 3(max 3) | 67 |
| 305 | FL | 11 | 3 | 2 | 8 | 2 | 62.5 |
| 415 | CA | 15 | 3 | 1 | 13 | 1 | 59.8 |
| 713 | TX | 8 | 3 | 2 | 5 | 2 | 57 |
| 214 | TX | 6 | 2 | 3 | 2 | 3(max 3) | 55.9 |
| 301 | MD | 6 | 3 | 2 | 3 | 2 | 53.4 |
| 201 | NJ | 10 | 3 | 1 | 8 | 1 | 50.7 |
| 312 | IL | 9 | 3 | 1 | 7 | 1 | 48.9 |
| 617 | MA | 8 | 3 | 1 | 6 | 1 | 47 |
| 303 | CO | 6 | 2 | 2 | 3 | 2 | 45.9 |
| 313 | MI | 7 | 3 | 1 | 5 | 1 | 45.2 |
| 919 | NC | 7 | 3 | 1 | 5 | 1 | 45.2 |
| 602 | AZ | 5 | 2 | 2 | 2 | 2 | 44.1 |
| 215 | PA | 6 | 3 | 1 | 4 | 1 | 43.4 |
| 205 | AL | 7 | 2 | 1 | 5 | 1 | 37.7 |
| 512 | TX | 7 | 2 | 1 | 5 | 1 | 37.7 |
| 615 | TN | 6 | 2 | 1 | 4 | 1 | 35.9 |
| 803 | SC | 6 | 2 | 1 | 4 | 1 | 35.9 |
| 813 | FL | 6 | 2 | 1 | 4 | 1 | 35.9 |
| 904 | FL | 6 | 2 | 1 | 4 | 1 | 35.9 |
| 914 | NY | 7 | 3 | 0 | 6 | 0 | 35.2 |
| 314 | MO | 5 | 2 | 1 | 3 | 1 | 34.1 |
| 601 | MS | 5 | 2 | 1 | 3 | 1 | 34.1 |
| 703 | VA | 5 | 2 | 1 | 3 | 1 | 34.1 |
| 804 | VA | 5 | 2 | 1 | 3 | 1 | 34.1 |
| 203 | CT | 4 | 2 | 1 | 2 | 1 | 32.3 |
| 502 | KY | 4 | 2 | 1 | 2 | 1 | 32.3 |
| 503 | OR | 4 | 2 | 1 | 2 | 1 | 32.3 |
| 513 | OH | 4 | 2 | 1 | 2 | 1 | 32.3 |
| 614 | OH | 4 | 2 | 1 | 2 | 1 | 32.3 |
| 717 | PA | 4 | 2 | 1 | 2 | 1 | 32.3 |
| 916 | CA | 4 | 2 | 1 | 2 | 1 | 32.3 |
| 817 | TX | 4 | 1 | 1 | 2 | 1 | 24.8 |
| 912 | GA | 4 | 1 | 1 | 2 | 1 | 24.8 |
| 206 | WA | 5 | 2 | 0 | 4 | 0 | 24.1 |
| 216 | OH | 5 | 2 | 0 | 4 | 0 | 24.1 |
| 317 | IN | 3 | 1 | 1 | 1 | 1 | 23 |
| 318 | LA | 3 | 1 | 1 | 1 | 1 | 23 |
| 405 | OK | 3 | 1 | 1 | 1 | 1 | 23 |
| 412 | PA | 3 | 1 | 1 | 1 | 1 | 23 |
| 702 | NV | 3 | 1 | 1 | 1 | 1 | 23 |
| 704 | NC | 3 | 1 | 1 | 1 | 1 | 23 |
| 716 | NY | 3 | 1 | 1 | 1 | 1 | 23 |
| 801 | UT | 3 | 1 | 1 | 1 | 1 | 23 |
| 816 | MO | 3 | 1 | 1 | 1 | 1 | 23 |
| 404 | GA | 4 | 2 | 0 | 3 | 0 | 22.3 |
| 414 | WI | 4 | 2 | 0 | 3 | 0 | 22.3 |
| 501 | AR | 4 | 2 | 0 | 3 | 0 | 22.3 |
| 202 | DC | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 208 | ID | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 217 | IL | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 304 | WV | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 309 | IL | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 315 | NY | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 402 | NE | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 419 | OH | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 507 | MN | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 518 | NY | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 608 | WI | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 618 | IL | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 715 | WI | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 787 | PR | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 812 | IN | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 814 | PA | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 815 | IL | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 918 | OK | 2 | 1 | 1 | 0 | 1 | 21.1 |
| 612 | MN | 5 | 1 | 0 | 4 | 0 | 16.6 |
| 219 | IN | 3 | 1 | 0 | 2 | 0 | 13 |
| 504 | LA | 3 | 1 | 0 | 2 | 0 | 13 |
| 616 | MI | 3 | 1 | 0 | 2 | 0 | 13 |
| 915 | TX | 3 | 1 | 0 | 2 | 0 | 13 |
| 316 | KS | 2 | 1 | 0 | 1 | 0 | 11.1 |
| 319 | IA | 2 | 1 | 0 | 1 | 0 | 11.1 |
| 505 | NM | 2 | 1 | 0 | 1 | 0 | 11.1 |
| 515 | IA | 2 | 1 | 0 | 1 | 0 | 11.1 |
| 517 | MI | 2 | 1 | 0 | 1 | 0 | 11.1 |
| 606 | KY | 2 | 1 | 0 | 1 | 0 | 11.1 |
| 901 | TN | 2 | 1 | 0 | 1 | 0 | 11.1 |
| 913 | KS | 2 | 1 | 0 | 1 | 0 | 11.1 |
| 207 | ME | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 218 | MN | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 302 | DE | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 307 | WY | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 308 | NE | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 401 | RI | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 406 | MT | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 413 | MA | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 417 | MO | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 509 | WA | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 603 | NH | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 605 | SD | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 607 | NY | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 701 | ND | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 712 | IA | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 802 | VT | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 806 | TX | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 808 | HI | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 906 | MI | 1 | 0 | 0 | 0 | 0 | 1.8 |
| 907 | AK | 1 | 0 | 0 | 0 | 0 | 1.8 |
Showing 100 of 100 families. Click column headers to sort.
Methodology
Data source: Family tree relationships from our proprietary NANPA-derived dataset, cross-referenced with official area code assignment records. Regenerable with scripts/generate-family-complexity.py from data/family-tree.json.
Definitions: A full lineage counts every descendant of a root code through both splits and overlays (the largest lineage, 213, spans 22 codes). A split chain follows only geographic split edges — overlays are excluded (the longest chain, 213, runs 213 → 714 → 619 → 760). Overlay complexes — groups of codes sharing one footprint — are tracked separately from split families; codes that belong to overlay cycles but never spawned splits appear only in their overlay complex, not in any split-family entry above.
Coverage: 100 root families containing 373 total area codes. Each code is classified as root, split, or overlay based on its role in the NANP numbering plan.
Complexity score: A composite metric combining family size (40% weight), tree depth (30%), and overlay group count (30%). Each dimension is normalized to its observed maximum across all root families (size 22, depth 4, overlays 3) on a 0–100 scale; the highest-scoring family (213) reaches 80.
Split chains: Traced by following parent references from each split code back to its root. Only non-overlay (geographic split) codes are included in chain calculations.
Overlay groups: Groups of codes that share the same geographic footprint. A family with many overlay groups has multiple overlapping codes in the same region, indicating repeated number exhaustion.
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