St. Louis County, MO Zoning: County Code vs. 88 Cities

St. Louis County genuinely has zoning -- a real Department of Planning, a real Zoning Ordinance, and a real Non-Urban district with a 3-acre minimum. The catch is that this county-level system only governs unincorporated land, and 88 separate cities each run their own zoning code on top of it.

This page covers what's specific to St. Louis County. For the general explanation, see the national guide.

The county-level district system and where the Non-Urban district fits

St. Louis County's Department of Planning administers Chapter 1003 of the county code, the Zoning Ordinance, which was originally adopted in 1965 and has been amended repeatedly since. Like most zoning ordinances, it sets out a district system running from lower-density residential districts up through commercial and industrial classifications, with each district carrying its own permitted-use list, setback standards, and lot-area minimums. For a land buyer specifically interested in acreage rather than a standard residential lot, the district that matters most is the "NU" (Non-Urban) district, which generally does not permit the creation of a new lot smaller than 3 acres -- with narrow exceptions carved out for uses like fire and police stations, day nurseries, and local public-utility facilities. That 3-acre floor is the closest thing to a rural-acreage zoning rule this dense, heavily suburbanized county has.

In practice, NU-zoned unincorporated land is concentrated in pockets toward the county's western and southwestern edges, and even there it competes with incorporated cities like Wildwood -- itself formed in 1995 specifically to preserve large-lot, lower-density character in that part of the county through its own municipal code rather than the county's. Don't assume a listing described as "acreage" or "rural" in St. Louis County is actually unincorporated NU land; confirm the zoning jurisdiction and district directly with the county's Department of Planning ((314) 615-2520) before treating a 3-acre minimum, or any other NU-district standard, as settled for a specific parcel.

Subdividing land: Chapter 1005 and the minor/major distinction

If you're looking at a larger unincorporated tract with an eye toward splitting it later, the county's Subdivision Ordinance (Chapter 1005) governs how that happens. Plats are reviewed by the Department of Planning in coordination with the Department of Transportation and Public Works' Chief of Surveys, under Section 1005.360 of the county code. The ordinance draws a distinction between smaller "minor" subdivisions (a limited number of resulting lots, generally handled through a lighter-weight boundary-adjustment or lot-split process) and larger "major" subdivisions requiring full preliminary and final plat review -- a meaningfully different timeline and paperwork burden depending on which category your split falls into. The county publishes separate checklists for a straightforward boundary adjustment or lot consolidation versus a full subdivision into five or more lots, so identify which process actually fits your plan before assuming either a quick administrative approval or a lengthy plat-review process applies.

Because this is real, actively administered zoning and subdivision review -- not the informal, largely unregulated environment found in most rural Missouri counties -- budget real time and, likely, professional survey and engineering help into any subdivision plan here. Confirm the current fee schedule, required supporting materials (drainage plans, utility confirmations, and similar), and expected review timeline directly with the Department of Planning rather than assuming a rural county's lighter-touch process will apply.

Figuring out which of 89 rulebooks applies to your parcel

The single most important zoning question for any St. Louis County parcel is jurisdictional, not substantive: is this land unincorporated (governed by the county's own Chapter 1003/1005 system) or does it sit inside one of the county's 88 incorporated municipalities, each of which enforces its own separate zoning and building code? Cities as large as Chesterfield and Florissant and as small as some of the county's numerous small municipalities all administer independently, meaning the same acreage, the same setback question, or the same accessory-structure rule can have 89 different answers depending on exactly where the parcel line falls. A property just across a municipal boundary from another otherwise-similar parcel can face a completely different approval process, fee schedule, and even architectural-review requirement.

Start by confirming jurisdiction through the county's GIS parcel-viewer tools or by calling the Department of Planning directly with the parcel's address or parcel number -- county staff can tell you whether a given address is unincorporated or which city it falls within, even if you then need to redirect follow-up questions to that city's own planning office. Don't rely on a real estate listing's description of "county" versus a city name, since colloquial usage (a mailing address referencing a city name, for instance) doesn't always match the parcel's actual incorporation status for zoning purposes.

Zoning in St. Louis County, Missouri

The county-level district system and where the Non-Urban district fits

Subdividing land: Chapter 1005 and the minor/major distinction

Figuring out which of 89 rulebooks applies to your parcel

Ready to talk to someone who knows land?