Northern Missouri
Marion County is a zoned county, so permits can apply outside town
Marion County's county coordinator says the county is zoned, building permits are required, and on-site wastewater permits come from the health department.
Do not assume rural Marion County is permit-free. The county coordinator page says Marion County is a zoned county, that building permits are required in the county, and that on-site wastewater permits are required from the Marion County Health Department.
That is a practical pre-closing question for land, additions, outbuildings, and rural homes. A property may be outside Hannibal or Palmyra city limits and still have county zoning or wastewater steps.
The first move is to identify the exact jurisdiction: city, county, subdivision, health department, and any utility or road layer. Then ask the county coordinator or health department what permit history, inspections, or applications apply. This is especially useful when a listing says “unincorporated” as if that means no local rules.
References
Where this fits: this note belongs to Marion County. See every local note for the county on its page.