Natrona County, WY zoning map, flood zone and property lines by address
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Towns in Natrona County: Casper, Mills, Evansville.
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's countywide study for Natrona County has 148 FIRM panels, the newest effective May 2015; 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 Natrona 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 Wyoming statewide parcels (2026 tax year), from county assessors, so a Natrona lot shows the same lines the county assessor draws. Natrona County covers about 3,417,942 acres of land and 22,481 acres of water.
Mapped lines are approximate. The Natrona County assessor keeps the parcel record (Natrona County website); a licensed surveyor sets the true corners.
Zoning
Natrona County zones its unincorporated land, and Casper, Mills, Evansville each zone the land inside their limits. ParcelSheet shows the use the county assessor lists for the lot and links the county planning and zoning office for the district, the uses it allows and the lot size it needs.
ADU and guest houses
Under Wyoming's county planning and zoning law (Wyoming Statutes 18-5-201 through 18-5-208), local governments can allow an accessory dwelling unit on a lot with a house. Whether a Natrona lot can add one depends on its district; the county planning and zoning 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. Natrona County is soil survey area WY625, Natrona County Area, Wyoming, last updated September 2026, on Web Soil Survey.
A new or changed septic system in Natrona County needs a permit from the Natrona County small wastewater permitting authority (the county, or Wyoming DEQ in counties without a delegated program).
Setbacks
Setbacks in Natrona 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 Casper, Mills, Evansville for land inside their limits.
Hazards that apply
- Wetlands and wildfire. ParcelSheet shows the National Wetlands Inventory near a Natrona lot and the Forest Service wildfire hazard rating at it.
Questions
Is my house in a flood zone in Natrona County?
Type the address in the box above and ParcelSheet reads FEMA's flood zone at the lot's center. FEMA's countywide flood map for Natrona County has 148 panels, the newest effective May 2015. A lender or insurer uses the official FIRM panel; FEMA's Map Service Center has it.
How do I find property lines in Natrona County?
Open the Wyoming map, type the address, and the parcel outline from the Natrona County assessor 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 Natrona County?
Zoning in Natrona County is set by the county for unincorporated land and by each city (such as Casper, Mills) inside its own limits. ParcelSheet shows the use code the county assessor lists and links the office that sets the zoning; the planning office has the final word.
Can I build an ADU in Natrona County?
Under Wyoming's county planning and zoning law (Wyoming Statutes 18-5-201 through 18-5-208), counties and cities can allow an accessory dwelling unit, and each sets its own rules. In Natrona 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 Natrona County?
Yes. A new or changed septic system in Natrona County needs a permit from the Natrona County small wastewater permitting authority (the county, or Wyoming DEQ in counties without a delegated program). ParcelSheet shows the USDA soil survey's septic rating at the lot, from survey area WY625 (Natrona County Area, Wyoming).
What can I build on 5 acres in Natrona County?
Zoning in Natrona County is set by the county for unincorporated land and each city inside its own limits (such as Casper, Mills). 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 Natrona County website.
What are the residential setbacks in Natrona County (2026)?
Setbacks in Natrona 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 Natrona County website.
Next to Natrona County: Carbon County, Converse County, Fremont County, Johnson County, Washakie County.
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