ZIP codes

ZIP codes in Southeastern Connecticut Planning Region, Connecticut

Southeastern Connecticut Planning Region has 33 ZIP codes. 27 lie entirely inside it and 6 are shared with neighboring counties, so part of their land and their people are elsewhere. About 279,320 people live in the parts inside it (ACS 2020–2024).

By the All Map Tools Team

ZIP codes: 33; 1 more just touches the border (under 1% of their land)
Entirely inside: 27; 99% or more of their land
Shared with other counties: 6; Most with Northeastern Connecticut Planning Region (3)
Most populated ZIP: 06360; 37,216 people · Norwich
Least populated ZIP: 06338; 27 people · Mashantucket; 1 more with nobody living there
Largest ZIP by land: 06415; 56 sq mi · Colchester

Map of the ZIP codes in Southeastern Connecticut Planning Region

Entirely in the county (99% or more of its land)
Shared, mostly in this county
Shared, mostly in other counties
Neighboring counties

Open in the interactive tool

Each area is a ZIP code with its number where it fits. Hover over one to see its name.

All ZIP codes in Southeastern Connecticut Planning Region

33 ZIP codes in Southeastern Connecticut Planning Region, CT, by number
ZIP code	Main city	Population	Land in the county	Residents in the county
06226	Willimantic	19,344	98%	≈ 19,075
06249	—	7,116	100%	7,116
06254	—	2,004	100%	2,004
06256	Willimantic	1,704	99.5%	≈ 1,703
06266	South Windham	222	100%	222
06280	South Windham	3,110	76%	≈ 3,016
06320	New London	27,703	100%	27,703
06330	Baltic	3,327	75%	≈ 2,948
06333	—	7,389	100%	7,389
06334	—	2,249	100%	2,249
06335	Gales Ferry	6,307	100%	6,307
06336	—	44	100%	44
06338	Mashantucket	27	100%	27
06339	Mashantucket	9,113	100%	9,113
06340	Conning Towers-Nautilus Park	29,863	100%	29,863
06350	—	121	100%	121
06351	Jewett City	15,760	97%	≈ 15,660
06353	Oxoboxo River	439	100%	439
06355	Old Mystic	12,173	100%	12,173
06357	Niantic	11,332	100%	11,332
06359	—	5,160	100%	5,160
06360	Norwich	37,216	100%	37,216
06365	Mashantucket	4,807	100%	4,807
06370	Oxoboxo River	7,327	100%	7,327
06375	—	3,670	100%	3,670
06378	Mystic	5,555	100%	5,555
06379	Pawcatuck	9,017	100%	9,017
06380	Norwich	2,757	100%	2,757
06382	Oxoboxo River	10,143	100%	10,143
06385	Waterford	15,966	100%	15,966
06389	Norwich	0	100%	0
06415	Colchester	16,038	87%	≈ 14,931
06420	—	4,368	98%	≈ 4,265

They also touch the county with under 1% of their land, so they aren’t counted: 06331.

ZIP codes shared with other counties

These 6 ZIP codes have part of their land in another county. The first figure is the share of their land in Southeastern Connecticut Planning Region; then, where the rest lies.

06226 (Willimantic): 98% here; 2.2% in Capitol Planning Region.
06280 (South Windham): 76% here; 24% in Northeastern Connecticut Planning Region.
06330 (Baltic): 75% here; 25% in Northeastern Connecticut Planning Region.
06351 (Jewett City): 97% here; 2.9% in Northeastern Connecticut Planning Region.
06415 (Colchester): 87% here; 13% in Lower Connecticut River Valley Planning Region.
06420: 98% here; 2.1% in Lower Connecticut River Valley Planning Region.

Cities and prefixes

By main city (the city, town or CDP each ZIP shares the most land with), the ones with the most are Mashantucket (3), Norwich (3), Oxoboxo River (3), South Windham (2), Willimantic (2), and Baltic (1); 16 places in all.

They start with 3 different three-digit prefixes, one per USPS sorting center: 062, 063, and 064.

Neighboring counties

Each one with its ZIP codes. Those without a page of their own open in the tool.

Tools for this county

ZIP codes by county or city The same ZIP codes on an interactive map, with the list as CSV or to copy County map with cities Its cities, towns and CDPs with their population ZIP codes in a radius The ZIP codes within 10 miles of its center, or any distance you like

Sources

U.S. Census Bureau, 2020 ZCTA to County, ZCTA to Place and ZCTA to Census Tract Relationship Files (and the 2022 County Subdivision to ZCTA file for Connecticut). Public domain.
U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates, table B01003 (population of each ZIP code, census tract and Connecticut town). Public domain.
U.S. Census Bureau, Vintage 2025 Population Estimates (county population) and 2025 Gazetteer Files (land area and interior point of each ZIP code). Public domain.
U.S. Census Bureau, Cartographic Boundary Files: ZCTAs 2020 and counties 2025, 1:500,000; county adjacency file 2025. Public domain.

How we count. ZIP codes here are the Census Bureau’s ZIP Code Tabulation Areas (ZCTAs), the areas it draws to match USPS ZIP codes; ZIPs with no area of their own (PO boxes, single buildings) aren’t included. A ZIP can cross county lines: “Land in the county” is the exact share of its land inside, from the Census relationship files. “Residents in the county” is the whole ZIP for those entirely inside; for shared ones it’s an estimate, spreading the people of each census tract over the land it shares with the ZIP. Population: ACS 2020–2024. Methodology.

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