A Chicago zoning district reads like a license plate — RS-3, B3-2, PD 1234 — and once you know the pattern it tells you, at a glance, what can legally be built on a lot. The zoning code is the single most important fact about a parcel for anyone thinking about building, adding a unit, or opening a business.
The letters: the district family
The leading letter(s) name the family of use the district is for:
RS — Residential Single-unit (detached houses). RT — Residential Two-flat, Townhouse, and Multi-unit (the classic Chicago two- and three-flat). RM — Residential Multi-unit (larger apartment buildings). B — Business (storefront retail with dwellings above, the neighborhood main-street pattern). C — Commercial (heavier commercial, auto-oriented uses). M — Manufacturing (industrial). DX/DC/DR/DS — Downtown districts. And PD — a Planned Development, a custom zoning negotiated for one big site.
The number: the intensity
The number after the dash is, roughly, how much you can build — it maps to a floor-area ratio (FAR) bracket and related bulk limits. Higher number, more density. So RS-1 is the lowest-density single-family district (big lots, low coverage) and RS-3 allows a more typical city lot; B3-2 is a community-shopping district at a moderate FAR, while B3-5 on the same street would allow a much taller mixed-use building. The letter tells you what; the number tells you how much.
Planned Developments are the exception
When a parcel is zoned PD (Planned Development), the standard district table does not apply — the rules live in a project-specific ordinance the City Council passed for that site. Stadiums, hospital campuses, and large mixed-use projects are almost always PDs. Wrigley Field, for instance, sits in a Planned Development, not a plain business district. If your address is a PD, the zoning map will name the PD number, and the real rules are in that ordinance.
Why it changes — and how to check
Zoning is not static. An alderperson can introduce a zoning change (an “upzone” or “downzone”) for parcels in their ward, and the City’s ADU rules have been loosening what a residential district allows. That is why you check the current district for a specific address rather than assuming the block. Search above to resolve an address to its parcel and its zoning, or open the Chicago zoning map to see what can be built, and the zoning-by-community-area map to see how much of a neighborhood is locked to single-family.
Source: City of Chicago zoning districts (public records), resolved to the parcel. Zoning determinations for permits are made by the City; confirm with the Department of Planning and Development before relying on it.