Blog · October 14, 2026 · Idaho
Using the Custer County Flood Zone Map
The zone on FEMA's map affects insurance, building and resale near Lost River.
Main page: Custer County, ID GIS & Parcel Viewer (official map link, county facts and neighboring maps).
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Before an offer near Salmon River, check the Custer County flood zone map: the zone on that map shapes insurance, building rules and resale. What this Custer County guide covers: finding the address on FEMA's map, reading the zone codes, and confirming the outline on the county map.
Getting started with the Custer County flood zone map
If you're looking near Big Lost River, flood zones come from FEMA's Flood Map Service Center: enter the street address, and choose the dynamic map. A tract near Big Lost River without an address is still easy to locate: pan from the closest town then click the parcel area.
Where the parcel data lives
Go first to the Idaho statewide Parcels layer in ArcGIS Map Viewer; it maps each assessed parcel from Lost River Range to Stanley. Without an address in hand, follow the nearest road on the aerial and select the outline, for land near Mackay included. If you're looking near Clayton, write down the parcel ID from that panel; each office in the county will want it.
Who handles what
Recorded documents for a parcel near Lost River Range are with the County Recorder (the county clerk serves as recorder), usually searchable by name or document number. Questions about what you can build around Lost River need the planning or permitting office, and the answer depends on jurisdiction.
Field tips
The parcel map usually runs in a mobile browser, useful out on a road near Lost River Range, but coverage can be spotty out of town. A screenshot of the parcel near Goldburg with its ID helps when you meet an owner or agent.
Zones on the Custer County flood zone map
An AE label comes with a base flood elevation, and an unnumbered A zone has none; surveyors near Stanley use that number. For a home near Big Lost River, a shaded X area marks moderate flood hazard, roughly the 100- to 500-year range; plain X, or C on older maps, means minimal mapped risk.
Lining it up with the parcel map
FEMA's map shows zones but not ownership, so check the Idaho statewide Parcels layer in ArcGIS Map Viewer too to confirm you have the right parcel near Salmon River.
A quick look at the area
Challis serves as the county seat, which is where the courthouse records live. You'll also find Clayton, Lost River, Mackay, and Stanley, where town lots give way to larger tracts. About 4,523 people call Custer County home (Census Bureau estimate, 2023) across about 4,922 square miles. Custer County was organized in 1881, so old deeds can run back a long way. Features like Lost River Range, Salmon River, and Challis National Forest make handy reference points on the map.
Reading the legal description
Idaho follows the Public Land Survey System, which means a tract near Lost River Range is described by section, township and range. Each section is nominally a mile square, about 640 acres, and a township holds 36 of them, though real sections near Big Lost River vary in size. Write down the legal description for the tract near Challis before you request a deed or survey.
Water near Mackay
Creeks and ditches near Mackay aren't always studied in detail, so walk the land after rain. Wet ground around Lost River is a separate issue from flood zones; check the National Wetlands Inventory mapper for a first look.
Land on the county line
Custer County borders Blaine County, Boise County, Butte County, Elmore County, and Lemhi County; every one of them runs a separate parcel map. A tract near the line by Ellis can be split across two assessors' files, so look at the adjacent map as well. Closer to Goldburg, the Platbookmapper state page links every bordering county map across Idaho.
What a flood zone means for a buyer
For land near Lost River, an Elevation Certificate from a surveyor helps: it records the building's elevation against the base flood. Remodeling a house in a zone near Goldburg can trigger elevation rules; call the permitting office early.
Questions to ask before you buy
Ask the listing agent for any Elevation Certificate for the house near Big Lost River; getting a quote early keeps the budget honest.
Before you lean on the lines
Closer to Mackay, acreage on the record is an estimate; only a licensed surveyor sets the real lines on the ground. For a home near Mackay, records update in batches, so a deed recorded last month can take weeks to appear.
Questions about the Custer County flood zone map
Can I see flood zones on the Idaho statewide Parcels layer in ArcGIS Map Viewer in Custer County?
Short answer: the parcel map near Salmon River might show FEMA zones, but FEMA's own map is the official source.
Can a property in Zone X near Salmon River flood?
X zones around Clayton are lower risk, not no risk, and floods still happen outside high-risk zones.
Is my property near Lost River in a flood zone?
FEMA's free map shows the zone for any spot near Big Lost River; no account is needed.
Can I challenge a flood zone near Salmon River?
Short answer: you can ask FEMA for a LOMA if surveyed elevations show the building near Salmon River is above the BFE, and lenders accept the result.
Is the parcel map a survey for land near Clayton?
In and around Ellis, parcel lines are tax drawings, not surveys; a survey sets the real corners
Open the official Custer County, ID parcel map See it in the Platbookmapper directory
Not a survey. County GIS and tax parcel maps are assessment and planning layers. They are not a substitute for a recorded plat, deed, or licensed survey, especially for fences, setbacks, or boundary disputes.