When was Elmore County founded?

Elmore County was founded in 1889, formed from Alturas County.

What is the county seat of Elmore County?

The county seat of Elmore County is Mountain Home.

Is there an online parcel map for Elmore County?

Yes. Idaho Department of Water Resources publishes a parcel map of 21,812 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Elmore County's boundary or name changed?

Elmore County was created in 1889 from Alturas County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Ada. County, Blaine County and Owyhee County.

Who issues building permits in Elmore County?

The county's page on building permits: Building Permit Requirements: – Elmore County, Idaho. Inside a city or town, ask that city first.

Is my lot in a flood zone?

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

County · code 16039

Elmore CountyIdaho

Elmore County is in Idaho and was created in 1889 from Alturas County, with Mountain Home as its seat.

Founded1889
County seatMountain Home
Land area3,075 sq mi + 26 sq mi water
Population28,666 2020 Census
Parcels mapped21,812 checked 16 October 2026

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

Updated 20 October 2026

Census outline · seat marked

History

Formed in 1889 from Alturas County

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

Elmore County was created by Idaho Territory from Alturas County on February 7, 1889, and continued as a county when Idaho became a state in 1890. The county expanded through additions from Blaine County in 1911, Owyhee County in 1930, and Ada County in 1948.

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

1889
Elmore County created Elmore created by Idaho Territory from Alturas (extinct).
from Alturas
7 February 1889 · Id. Terr. Laws 1888, 15th sess., pp. 33-36
1890
Became part of Idaho Elmore 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
1911
Gained territory Elmore gained from Blaine.
from Blaine
3 March 1911 · Id. Laws 1911, 11th sess., ch. 148/pp. 453-454
1930
Gained territory Elmore gained from Owyhee. Act approved 21 Feb 1929, became effective through a vote in the general election of 4 November 1930.
from Owyhee
4 November 1930 · Id. Laws 1929, 20th sess., ch. 47/pp. 59-66; Id. Code Ann. (1996), vol. 6, ch. 1, sec. 31-122 "Elmore Co."/p.32
1948
Gained territory Elmore gained from Ada. Act approved 10 Mar 1947, became effective through a vote in the general election of 2 November 1948.
from Ada.
2 November 1948 · Id. Laws 1947, 29th sess., ch. 150/pp. 352-359; Id. Code Ann. (1996), vol. 6, ch. 1, sec. 31-103 "Ada Co."/p. 4

Show all 10 changes (5 more, mostly small adjustments)

1889
Elmore County created Elmore created by Idaho Territory from Alturas (extinct).
from Alturas
7 February 1889 · Id. Terr. Laws 1888, 15th sess., pp. 33-36
1890
Became part of Idaho Elmore 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
Boundary clarified Elmore boundary with Ada redefined (no change).
with Adano change
9 February 1895 · Id. Laws 1895, 3rd sess., pp. 15-16
1899
Boundary clarified Elmore boundary with Ada redefined (no change).
with Adano change
14 February 1899 · Id. Laws 1899, 5th sess., p. 234
1911
Gained territory Elmore gained from Blaine.
from Blaine
3 March 1911 · Id. Laws 1911, 11th sess., ch. 148/pp. 453-454
1919
Boundary clarified Elmore redefined (no change).
no change
19 February 1919 · Id. Laws 1919, 15th sess., ch. 109/pp. 391-392
1923
Boundary clarified Elmore boundary with Ada redefined to run along range lines rather than from mouth of Bruneau River to mouth of Mores Creek (no change).
with Adano change
13 March 1923 · Id. Laws 1923, 17th sess., ch. 136/pp. 200-202
1925
Boundary clarified Elmore redefined (no change).
no change
10 February 1925 · Id. Laws 1925, 18th sess., ch. 26/pp. 38-39
1930
Gained territory Elmore gained from Owyhee. Act approved 21 Feb 1929, became effective through a vote in the general election of 4 November 1930.
from Owyhee
4 November 1930 · Id. Laws 1929, 20th sess., ch. 47/pp. 59-66; Id. Code Ann. (1996), vol. 6, ch. 1, sec. 31-122 "Elmore Co."/p.32
1948
Gained territory Elmore gained from Ada. Act approved 10 Mar 1947, became effective through a vote in the general election of 2 November 1948.
from Ada.
2 November 1948 · Id. Laws 1947, 29th sess., ch. 150/pp. 352-359; Id. Code Ann. (1996), vol. 6, ch. 1, sec. 31-103 "Ada Co."/p. 4

Land and parcels

What the maps cover in Elmore

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

Parcels Good enough

Lot lines and tax-map numbers for 21,812 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 Missing

No public address points layer found for Elmore County yet.
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

Elmore by the Census

Population

28,666 2020 Census count

Housing units

12,049 2020 Census count

Land area

3,075 square miles

Water area

26 square miles

People per sq mi

9 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

Who to ask before you build, dig or sell

Official county pages only. We link to them; we do not copy them, because they change.

Inside a city or town, permits usually come from that city rather than the county.

Permits

Building Permit Requirements: – Elmore County, Idahofrom elmorecounty.org

Zoning and code

Planning and zoningfrom elmorecounty.org · checked 13 October 2026
County Ordinances – Elmore County, Idahofrom elmorecounty.org
Zoning Mapfrom elmorecounty.org
Amended Zoning and Development Ordinance – Elmore County, Idahofrom elmorecounty.org

County government

County government
The official website of Elmore County.
elmorecounty.org

See your own lot on these maps

Open Elmore 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 Elmore County

When was Elmore County founded?: Elmore County was founded in 1889, formed from Alturas County.
What is the county seat of Elmore County?: The county seat of Elmore County is Mountain Home.
Is there an online parcel map for Elmore County?: Yes. Idaho Department of Water Resources publishes a parcel map of 21,812 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Elmore County's boundary or name changed?: Elmore County was created in 1889 from Alturas County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Ada. County, Blaine County and Owyhee County.
Who issues building permits in Elmore County?: The county's page on building permits: Building Permit Requirements: – Elmore County, Idaho. Inside a city or town, ask that city first.
Is my lot in a flood zone?: We do not have flood maps for Elmore County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

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