What is the county seat of Custer County?

The county seat of Custer County is Challis.

Is there an online parcel map for Custer County?

Yes. Idaho Department of Water Resources publishes a parcel map of 6,612 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Custer County's boundary or name changed?

Custer County was created in 1881 from Alturas County, Boise County and Lemhi County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Blaine County, Butte County and Idaho County.

Is my lot in a flood zone?

We do not have flood maps for Custer County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

County · code 16037

Custer CountyIdaho

Q: When was Custer County founded?

Custer County was founded in 1881, formed from Alturas County, Boise County and Lemhi County, and named after George Armstrong Custer.

Custer County is a county in central Idaho with its seat in Challis. The county was formed on April 1, 1881, from the territories of Alturas, Boise, and Lemhi, and was named after George Armstrong Custer.

Founded1881
County seatChallis
Named forGeorge Armstrong Custer
Land area4,922 sq mi + 16 sq mi water
Population4,275 2020 Census
Parcels mapped6,612 checked 16 October 2026

Open the free map Click any parcel in Custer County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated 20 October 2026

Census outline · seat marked

History

Formed in 1881 from Alturas County, Boise County and Lemhi County

An old deed may name a county that no longer exists, or a boundary that has since moved.

When Idaho became a state on February 4, 1890, Custer County was continued as a state county and Idaho Territory was eliminated. In 1925, Custer County exchanged territory with Blaine County, and in 1937 lost territory to Butte County.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries; the 5 that matter most are shown first.

1881
Custer County created Custer created by Idaho Territory from Alturas (extinct), Boise, and Lemhi.
from Alturas from Boisefrom Lemhi
1 April 1881 · Id. Terr. Laws 1880, 11th sess., pp. 340-345
1889
Gained territory Custer gained from Idaho.
from Idaho
4 February 1889 · Id. Terr. Laws 1888, 15th sess., pp. 22-23
1890
Became part of Idaho Custer continued as an Idaho county when the state of Idaho admitted to the Union and Idaho Territory eliminated. 3 July 1890 · U.S. Stat., vol. 26, ch. 656 [1890]/pp. 215-219; Van Zandt, 156
1925
Exchanged territory Custer exchanged with Blaine.
with Blaine
13 March 1925 · Id. Laws 1925, 18th sess., ch. 189/pp. 345-348
1937
Lost territory Custer lost to Butte.
to Butte
15 March 1937 · Id. Laws 1937, 21st sess., ch. 138/pp. 222-224

Show all 9 changes (4 more, mostly small adjustments)

1881
Custer County created Custer created by Idaho Territory from Alturas (extinct), Boise, and Lemhi.
from Alturas from Boisefrom Lemhi
1 April 1881 · Id. Terr. Laws 1880, 11th sess., pp. 340-345
1887
Boundary clarified Custer boundaries redefined (no change).
no change
1 June 1887 · Id. Terr. Laws 1887, comp., spec. and loc., 14th sess., pp. 128-129
1889
Gained territory Custer gained from Idaho.
from Idaho
4 February 1889 · Id. Terr. Laws 1888, 15th sess., pp. 22-23
1890
Became part of Idaho Custer continued as an Idaho county when the state of Idaho admitted to the Union and Idaho Territory eliminated. 3 July 1890 · U.S. Stat., vol. 26, ch. 656 [1890]/pp. 215-219; Van Zandt, 156
1895
Changed Legislature authorized Custer to annex territory from Blaine, dependent on a vote in the general election of 1896. No evidence that the vote ever took place; proposed annexation failed; cannot be mapped as described (no change).
Blaine
9 March 1895 · Id. Laws 1895, 3rd sess., pp.140-142; Id. Code Ann. (1996), vol. 6, ch. 1, sec. 31-121 "Custer Co."/p. 31
1899
Changed Legislature authorized Custer to annex territory from Blaine, dependent on a vote in the general election of 1900. Proposed annexation failed in referendum; cannot be mapped as described (no change).
Blaine
14 February 1899 · Id. Laws 1899, 5th sess., p. 271; Id. Code Ann. (1996), vol. 6, ch. 1, sec. 31-109 "Blaine Co."/p. 16
1925
Exchanged territory Custer exchanged with Blaine.
with Blaine
13 March 1925 · Id. Laws 1925, 18th sess., ch. 189/pp. 345-348
1931
Changed Legislature authorized Butte to annex territory from Custer, dependent on a vote in the general election of November 1932. No evidence this vote ever took place (no change).
Butte
27 February 1931 · Id. Laws 1931, 21st sess., ch. 63/pp. 106-113; Id. Code Ann. (1996), vol. 6, ch. 1, sec. 31-114 "Butte Co."/p. 21
1937
Lost territory Custer lost to Butte.
to Butte
15 March 1937 · Id. Laws 1937, 21st sess., ch. 138/pp. 222-224

Land and parcels

What the maps cover in Custer

Who publishes each layer, how good it is, and when we last checked.

Parcels Good enough

Lot lines and tax-map numbers for 6,612 parcels from Idaho Department of Water Resources. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
checked 16 October 2026
Address points Good enough

One point per address, 4,593 in all from Custer County.
checked 14 October 2026
Buildings Reference

Roof outlines traced from aerial imagery from FEMA Response Geospatial Office with Oak Ridge National Laboratory (ORNL). Good for seeing what is on a lot; not accurate enough to set a fence from.
checked 18 October 2026

Official: from the office that keeps the record
Good enough: a reliable statewide or national copy
Fallback: a guide only; check the official record
Missing: nothing public found yet

People and land

Custer by the Census

Population

4,275 2020 Census count

Housing units

3,021 2020 Census count

Land area

4,922 square miles

Water area

16 square miles

People per sq mi

<1 population ÷ land area

Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.

Rules and offices

Custer County's official site

We have found the county's site but not its offices yet; start there.

County government

County government
The official website of Custer County.
co.custer.id.us

See your own lot on these maps

Open Custer County on Parcel Chart's free map and click your parcel. Save it with a free account; the full record of your place (site map, projects, documents) is Pro, in early access.

Open the free map no sign-in Pro early access

Questions

Common questions about Custer County

When was Custer County founded?: Custer County was founded in 1881, formed from Alturas County, Boise County and Lemhi County, and named after George Armstrong Custer.
What is the county seat of Custer County?: The county seat of Custer County is Challis.
Is there an online parcel map for Custer County?: Yes. Idaho Department of Water Resources publishes a parcel map of 6,612 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Custer County's boundary or name changed?: Custer County was created in 1881 from Alturas County, Boise County and Lemhi County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Blaine County, Butte County and Idaho County.
Is my lot in a flood zone?: We do not have flood maps for Custer County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby