St. Clair County, IL Outdoor Lighting: Dark Sky Rules (2026)

Section 40-4-120 sets the dark-sky standard for the AO-1 District only, the airport-environs overlay reaching parts of unincorporated St. Clair County near Scott AFB and MidAmerica St. Louis Airport; it does not apply county-wide. Subsection (A)(1) requires the light source of every outdoor fixture on non-residential and multi-family land to be "fully shielded and downward facing so as not to allow any light above the horizontal, as measured at the luminaire," and subsection (A)(4) requires that shielding be "installed and maintained in such a manner that the shielding is effective," so a fixture that starts compliant but is later mis-aimed or damaged falls out of compliance.

Single-family homes and agricultural uses are exempt under subsection (B), but only "provided that such uses do not affect the safety of the public or persons utilizing Scott Air Force Base or MidAmerica St. Louis Airport," so the exemption can be lost case by case. " Any AO-1 site plan or subdivision construction drawing must include a lighting plan under subsection (E) showing every fixture's location, both proposed and existing, plus manufacturer's catalog cuts. The Zoning Administrator enforces the standard, and Sec. 40-4-113(C) lets the Director order corrective action, including a stop-work order, if field inspection shows lighting isn't built to the approved plan.