Jefferson County, MT zoning map, flood zone and property lines by address
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Towns in Jefferson County: Montana City, Clancy, Boulder.
Flood zone by address
ParcelSheet reads FEMA's National Flood Hazard Layer at the lot: the zone, whether it is a high risk area where lenders ask for flood insurance, and the base flood elevation where FEMA lists one. FEMA has 53 FIRM panels covering Jefferson County, the newest effective December 2024; no coastal V zones are mapped in it.
The official panel and any Letter of Map Amendment are at FEMA's Map Service Center. An elevation certificate for a Jefferson house comes from a licensed surveyor and is often on file with the county or city building office.
Property lines
The parcel outline, parcel number and mapped size come from the Montana State Library, Montana Cadastral (MSDI), from Department of Revenue records, so a Jefferson lot shows the same lines the Montana Department of Revenue draws. Jefferson County covers about 1,060,478 acres of land and 1,546 acres of water.
Mapped lines are approximate. The Montana Department of Revenue keeps the parcel record (Jefferson County website); a licensed surveyor sets the true corners.
Zoning
Jefferson County zones its unincorporated land, and Boulder zones the land inside its limits. ParcelSheet shows the use the Montana Department of Revenue lists for the lot and links the county planning office for the district, the uses it allows and the lot size it needs.
ADU and guest houses
Under Montana's county zoning laws (Montana Code Annotated Title 76, Chapter 2, Parts 1 and 2), local governments can allow an accessory dwelling unit on a lot with a house. Whether a Jefferson lot can add one depends on its district; the county planning office has the rule. ParcelSheet shows the mapped lot size and the ground's slope, the first two things the question turns on.
Septic and soil
ParcelSheet reads the USDA soil survey at the lot: the soil's name, its septic absorption rating and whether it is prime farmland. Jefferson County is soil survey area MT627, Jefferson County Area and Part of Silver Bow County, Montana, last updated September 2026, on Web Soil Survey.
A new or changed septic system in Jefferson County needs a permit from the Jefferson County sanitarian (local health department, under Montana DEQ standards).
Setbacks
Setbacks in Jefferson County come from the zoning district: the front, side and rear distances a house must keep. ParcelSheet does not draw setback lines; the county zoning office gives them for the lot's district, and Boulder for land inside its limits.
Hazards that apply
- Wetlands and wildfire. ParcelSheet shows the National Wetlands Inventory near a Jefferson lot and the Forest Service wildfire hazard rating at it.
Questions
Is my house in a flood zone in Jefferson County?
Type the address in the box above and ParcelSheet reads FEMA's flood zone at the lot's center. FEMA has 53 flood map panels covering Jefferson County, the newest effective December 2024. A lender or insurer uses the official FIRM panel; FEMA's Map Service Center has it.
How do I find property lines in Jefferson County?
Open the Montana map, type the address, and the parcel outline from the Montana Department of Revenue shows on the map with its parcel number and mapped size. Mapped lines are approximate; only a licensed surveyor sets the true corners.
What is my property zoned in Jefferson County?
Zoning in Jefferson County is set by the county for unincorporated land and by each city (such as Boulder) inside its own limits. ParcelSheet shows the use code the Montana Department of Revenue lists and links the office that sets the zoning; the planning office has the final word.
Can I build an ADU in Jefferson County?
Under Montana's county zoning laws (Montana Code Annotated Title 76, Chapter 2, Parts 1 and 2), counties and cities can allow an accessory dwelling unit, and each sets its own rules. In Jefferson County ask the zoning office for the lot's district first; ParcelSheet shows the lot size as mapped so you can see the room you have.
Do I need a septic permit in Jefferson County?
Yes. A new or changed septic system in Jefferson County needs a permit from the Jefferson County sanitarian (local health department, under Montana DEQ standards). ParcelSheet shows the USDA soil survey's septic rating at the lot, from survey area MT627 (Jefferson County Area and Part of Silver Bow County, Montana).
What can I build on 5 acres in Jefferson County?
Zoning in Jefferson County is set by the county for unincorporated land and each city inside its own limits (such as Boulder). The zoning district decides the uses, how many homes and the smallest lot it allows on 5 acres. ParcelSheet shows the lot size as mapped and the use code on the parcel record; the planning office has the district and its rules. See the Jefferson County website.
What are the residential setbacks in Jefferson County (2026)?
Setbacks in Jefferson County come from the zoning code of the county, or of the city when the lot is inside city limits: the front, side and rear distances depend on the lot's district. ParcelSheet does not draw setback lines or give a number it did not read; the zoning office gives them for the district. See the Jefferson County website.
Next to Jefferson County: Broadwater County, Deer Lodge County, Gallatin County, Lewis and Clark County, Madison County, Powell County, Silver Bow County.
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