ZIP codes

ZIP codes in St. Charles County, Missouri

St. Charles County has 15 ZIP codes. 13 lie entirely inside it and 2 are shared with neighboring counties, so part of their land and their people are elsewhere. About 414,694 people live in the parts inside it (ACS 2020–2024).

By the All Map Tools Team

ZIP codes: 15; With 1% or more of their land inside
Entirely inside: 13; 99% or more of their land
Shared with other counties: 2; Most with Warren County (2)
Most populated ZIP: 63376; 74,962 people · St. Peters
Least populated ZIP: 63365; 51 people · New Melle
Largest ZIP by land: 63301; 84 sq mi · St. Charles

Map of the ZIP codes in St. Charles County

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 St. Charles County

15 ZIP codes in St. Charles County, MO, by number
ZIP code	Main city	Population	Land in the county	Residents in the county
63301	St. Charles	52,667	100%	52,667
63303	St. Charles	46,089	100%	46,089
63304	Weldon Spring	43,195	100%	43,195
63332	Augusta	1,651	100%	1,651
63341	Defiance	3,515	100%	3,515
63348	Foristell	10,394	78%	≈ 8,371
63357	Three Creeks	6,536	3.8%	≈ 231
63365	New Melle	51	100%	51
63366	O'Fallon	54,769	100%	54,769
63367	Lake St. Louis	29,725	100%	29,725
63368	O'Fallon	46,966	100%	46,966
63373	Portage Des Sioux	690	100%	690
63376	St. Peters	74,962	100%	74,962
63385	Wentzville	51,330	100%	51,330
63386	West Alton	482	100%	482

ZIP codes shared with other counties

These 2 ZIP codes have part of their land in another county. The first figure is the share of their land in St. Charles County; then, where the rest lies.

63348 (Foristell): 78% here; 19% in Warren County and 2.1% in Lincoln County.
63357 (Three Creeks): 3.8% here; 96% in Warren County.

Cities and prefixes

By main city (the city, town or CDP each ZIP shares the most land with), the ones with the most are O'Fallon (2), St. Charles (2), Augusta (1), Defiance (1), Foristell (1), and Lake St. Louis (1); 13 places in all.

All 15 start with the same three digits, 633: the prefix of the USPS sorting center that handles them.

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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