ZIP code 63121

ZIP 63121 is a mid-size town in St. Louis County, Missouri, with 24,571 residents counted in the Census American Community Survey 2019-2023 ACS 5-year estimates, which places it #72 of 1,035 ranked by population — larger than 93% of them. The median age here is 35.2 years against 39.1 nationally, a slightly younger profile than the country as a whole. Places under 65,000 residents only appear in the five-year release, never the one-year file, so these values pool sixty months of responses and lag the current year by design.

Households in ZIP 63121 earn a median of $41,285 a year, 47.4% below the national figure of $78,538. The median is the midpoint household, not an average, so a handful of very high earners cannot drag it upward the way they distort a mean. Poverty reaches 23.6% of residents here, well above the 12.4% national rate, which is the single clearest signal in this dataset that median income here is carried by a narrow band of households.

The typical owner-occupied home in ZIP 63121 is valued at $93,900, 69.1% below the national figure, while median gross rent runs $938 a month, 33.3% below the national figure, or roughly $11,256 across a full year. A household on the local median income would put about 27.3% of gross pay toward that rent against the federal 30% cost-burden threshold, so renting here is within the standard affordability guideline. The home-price-to-income ratio works out to 2.3×, against roughly 3.9× nationally, so purchase prices are unusually low against local pay, the pattern in places where supply is plentiful and wage growth has been flat. 52.9% of occupied homes are owner-occupied versus 65% nationally, so the market leans more heavily on renters. The rent line includes utilities paid by the tenant, a definition worth remembering when comparing it against a landlord's quoted rate.

All values below were released by the Census for this exact geography, with no gap-filling on our side. Small-area estimates still carry wider margins of error than state or national figures, so check the linked ACS tables before relying on them for lending, appraisal or legal work.

ZIP 63121 is tabulated inside St. Louis County, Missouri, one of 43 ZIP areas the Census publishes for that county and 1,035 across Missouri. This is a mid-sized suburban ZIP inside a county that is split across many delivery areas. County assignment on this page follows the largest share of the ZIP's land area, which matters where a delivery route crosses a county line: mail addressed to 63121 can be handled by a post office in a neighbouring county even though the tabulation area is filed here.

Against its own county, 63121 reports a median household income of $41,285, 52% below the $86,196 county median, and 32% below the $60,651 typical MO ZIP. Owner-occupied homes are valued at a median of $93,900, 66% below the county figure and 42% below the statewide ZIP median. Rent is reported gross — the contract amount plus tenant-paid utilities — at $938 a month, which is why it reads higher than the advertised rent on a listing for the same unit.

Missouri charges 4.225% statewide, and local governments overlapping 63121 may add county, city or special-district levies on top. We publish the state floor for this ZIP rather than guessing a combined figure, because ZIP boundaries and taxing-district boundaries were drawn for different purposes and do not line up.

Everything above comes from the Census Bureau American Community Survey 2019-2023 ACS 5-year estimates for this ZIP Code Tabulation Area, with sales tax rates traced to the state revenue agency. Five-year estimates pool sixty months of responses, so they are stable enough to compare 63121 with its neighbours but always trail the current year, and any value the Census suppressed for sample size is shown as unpublished rather than filled in with a model.