Which ZIP code in St. Charles County has the highest median age?

63341 (Defiance), at 48.6 (±2.6), among 11 ZIP codes with at least 1,000 residents.

Why are some ZIP codes missing?

ZIP codes with fewer than 1,000 residents are left out because their survey estimates swing too much to rank, and so are ZIP codes where the Census Bureau did not publish this figure.

Oldest ZIP codes in St. Charles County, MO

These are the 11 ZIP codes in St. Charles County with the highest median age, out of 11 with at least 1,000 residents. 63341 (Defiance, 48.6), 63348 (Foristell, 43.0) and 63332 (Augusta, 41.6) lead the list. There is no single "best" ZIP code in St. Charles County; the right one depends on who you want to reach, so the same ZIP codes are ranked several ways below.

Oldest ZIP codes in St. Charles County

Rank	ZIP	Mailing city	Median age	Residents	Households	Residential mailboxes
1	63341	Defiance	48.6 ±2.6	3,515	1,324	1,558
2	63348	Foristell	43.0 ±2.1	10,394	3,781	3,253
3	63332	Augusta	41.6 ±6.7	1,651	616	625
4	63303	Saint Charles	41.4 ±1.3	46,089	20,690	21,072
5	63376	Saint Peters	40.9 ±0.8	74,962	30,034	31,724
6	63304	Saint Charles	40.7 ±1.1	43,195	16,284	17,988
7	63366	O Fallon	40.4 ±1.3	54,769	20,967	21,505
8	63367	Lake Saint Louis	39.5 ±0.8	29,725	11,125	12,642
9	63301	Saint Charles	38.0 ±1.0	52,667	21,462	23,411
10	63385	Wentzville	38.0 ±1.4	51,330	18,106	21,803
11	63368	O Fallon	38.0 ±1.1	46,966	17,271	18,325

How we ranked them

Ranked by median age of all residents, highest first (ACS 5-year estimates, 2020–2024). ZIP codes need at least 1,000 residents to be ranked; 11 of 14 qualify.

Which of these to mail, and why

Older ZIP codes respond to health care, hearing and vision, Medicare plans, home safety, estate planning and services that come to the door.

The top five ZIP codes on this list hold 56,445 households, on 92 carrier routes with 58,232 residential mailboxes. Open any of them on the route map to see each carrier route's own figures before you choose.

Open 63341 on the EDDM route map

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Frequently asked questions

Which ZIP code in St. Charles County has the highest median age?: 63341 (Defiance), at 48.6 (±2.6), among 11 ZIP codes with at least 1,000 residents.
How is this ranking calculated?: Ranked by median age of all residents, highest first (ACS 5-year estimates, 2020–2024).
Why are some ZIP codes missing?: ZIP codes with fewer than 1,000 residents are left out because their survey estimates swing too much to rank, and so are ZIP codes where the Census Bureau did not publish this figure.

This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.