O'Brien County, IA zoning map, flood zone and property lines by address
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Towns in O'Brien County: Sheldon, Hartley, Sanborn.
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 O'Brien County has 41 FIRM panels, the newest effective December 2020; 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 an O'Brien 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 Iowa county parcel layers (each county publishes its own), so an O'Brien lot shows the same lines the county assessor draws. O'Brien County covers about 366,742 acres of land and 111 acres of water.
Mapped lines are approximate. The O'Brien County assessor keeps the parcel record (O'Brien County website); a licensed surveyor sets the true corners.
Zoning
O'Brien County zones its unincorporated land, and Sheldon, Hartley, Sanborn each zone the land inside their limits. ParcelSheet shows the use the county assessor lists for the lot and links the county zoning office for the district, the uses it allows and the lot size it needs.
ADU and guest houses
Under Iowa's county zoning law (Iowa Code Chapter 335), local governments can allow an accessory dwelling unit on a lot with a house. Whether an O'Brien lot can add one depends on its district; the county 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. O'Brien County is soil survey area IA141, O'Brien County, Iowa, last updated September 2026, on Web Soil Survey.
A new or changed septic system in O'Brien County needs a permit from the O'Brien County environmental health department (county board of health, under Iowa Department of Natural Resources rules).
Setbacks
Setbacks in O'Brien 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 Sheldon, Hartley, Sanborn for land inside their limits.
Hazards that apply
- Wetlands and wildfire. ParcelSheet shows the National Wetlands Inventory near an O'Brien lot and the Forest Service wildfire hazard rating at it.
Questions
Is my house in a flood zone in O'Brien 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 O'Brien County has 41 panels, the newest effective December 2020. A lender or insurer uses the official FIRM panel; FEMA's Map Service Center has it.
How do I find property lines in O'Brien County?
Open the Iowa map, type the address, and the parcel outline from the O'Brien 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 O'Brien County?
Zoning in O'Brien County is set by the county for unincorporated land and by each city (such as Sheldon, Hartley) 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 O'Brien County?
Under Iowa's county zoning law (Iowa Code Chapter 335), counties and cities can allow an accessory dwelling unit, and each sets its own rules. In O'Brien 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 O'Brien County?
Yes. A new or changed septic system in O'Brien County needs a permit from the O'Brien County environmental health department (county board of health, under Iowa Department of Natural Resources rules). ParcelSheet shows the USDA soil survey's septic rating at the lot, from survey area IA141 (O'Brien County, Iowa).
What can I build on 5 acres in O'Brien County?
Zoning in O'Brien County is set by the county for unincorporated land and each city inside its own limits (such as Sheldon, Hartley). 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 O'Brien County website.
What are the residential setbacks in O'Brien County (2026)?
Setbacks in O'Brien 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 O'Brien County website.
Next to O'Brien County: Cherokee County, Clay County, Osceola County, Sioux County.
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