St. Louis County Chapter 625 (Noise Control Code) governs noise in unincorporated areas. The code restricts lawn-care maintenance equipment to operation from 7:00 a.m. prevailing local time to sunset (when fitted with original-equivalent sound control devices). State law RSMo 574.010 (peace disturbance) backstops loud noise that knowingly disturbs another. Each of the 88+ municipalities in the county (Florissant, Kirkwood, Ferguson, etc.) sets its own quiet hours.
St. Louis County Revised Ordinances (SLCRO) Chapter 625 is the county Noise Control Code, applying in unincorporated St. Louis County. Section 625 limits lawn-care maintenance equipment to operation between 7:00 a.m. (prevailing local time) and sunset, and requires sound control devices equivalent to or better than original manufacturer equipment. The chapter regulates unreasonable noise rather than imposing a single nighttime decibel cap. Outside Chapter 625, RSMo 574.010 makes peace disturbance a state offense for unreasonably and knowingly making loud noise that disturbs another. Each incorporated city in the county (Florissant, Kirkwood, Ferguson, Chesterfield, Maryland Heights, University City, Webster Groves, Clayton, etc.) maintains its own noise code with potentially stricter quiet hours. Enforcement in unincorporated areas: St. Louis County Police, non-emergency (636) 529-8210.
Chapter 625 violations are typically prosecuted as ordinance violations in St. Louis County Municipal Court. Peace disturbance under RSMo 574.010 is a class B misdemeanor (up to 6 months jail, $1,000 fine) for a first conviction, class A misdemeanor for repeats (up to 1 year jail, $2,000 fine).
See how St. Louis County's quiet hours rules stack up against other locations.
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