When was Idaho County founded?

Idaho County was founded in 1861, formed from Shoshone County, and named after Idaho.

What is the county seat of Idaho County?

The county seat of Idaho County is Grangeville.

Is there an online parcel map for Idaho County?

Yes. Idaho Department of Water Resources publishes a parcel map of 28,590 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Idaho County's boundary or name changed?

Idaho County was created in 1861 from Shoshone County. Since then the Atlas of Historical County Boundaries records 21 later changes, chiefly involving Nez Perce County, Boise County and Lemhi County.

Who issues building permits in Idaho County?

The county's page on building permits: Concealed Weapons Permit FAQ – Official Idaho County Site. Inside a city or town, ask that city first.

Is my lot in a flood zone?

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

County · code 16049

Idaho CountyIdaho

Idaho County is located in Idaho and has its county seat in Grangeville. The county was established on December 20, 1861, and covers 8,477.5 square miles.

Founded1861
County seatGrangeville
Named forIdaho
Land area8,478 sq mi + 26 sq mi water
Population16,541 2020 Census
Parcels mapped28,590 checked 16 October 2026

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

Updated 20 October 2026

Census outline · seat marked

History

Formed in 1861 from Shoshone County

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

Idaho County was created by Washington Territory on December 20, 1861, from Shoshone County and initially included parts of present Montana, Idaho, and Wyoming. On January 12, 1863, Idaho County lost territory to the creation of Boise County. On March 3, 1863, Idaho County became a county in Idaho Territory when the United States created Idaho Territory. Idaho County continued as a county in the state of Idaho when it was admitted to the Union on July 3, 1890.

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

1861
Idaho County created Idaho created by Washington Territory from Shoshone; included parts of present Idaho, Montana, and Wyoming.
from Shoshone
20 December 1861 · Wash. Terr. Laws 1861-1862, 9th sess., p. 3
1863
Lost territory Idaho lost to creation of Boise.
to Boise
12 January 1863 · Wash. Terr. Laws 1862, 10th sess., pp. 3-4
1863
Became part of Idaho Idaho became an Idaho Territory county when the United States created Idaho Territory from Dakota, Nebraska, and Washington Territories. 3 March 1863 · U.S. Stat., vol. 12, ch. 117 [1863]/pp. 808-814; Van Zandt, 156-158
1864
Lost territory Idaho lost to creation of Deer Lodge (Montana), and lost to Missoula (Montana).
to Deer Lodge (Mont.)to Missoula (Mont.)
16 January 1864 · Id. Terr. Laws 1863, loc. and spec., 1st sess., sec. 1/p. 674
1890
Became part of Idaho Idaho 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

Show all 27 changes (22 more)

1861
Idaho County created Idaho created by Washington Territory from Shoshone; included parts of present Idaho, Montana, and Wyoming.
from Shoshone
20 December 1861 · Wash. Terr. Laws 1861-1862, 9th sess., p. 3
1863
Lost territory Idaho lost to creation of Boise.
to Boise
12 January 1863 · Wash. Terr. Laws 1862, 10th sess., pp. 3-4
1863
Became part of Idaho Idaho became an Idaho Territory county when the United States created Idaho Territory from Dakota, Nebraska, and Washington Territories. 3 March 1863 · U.S. Stat., vol. 12, ch. 117 [1863]/pp. 808-814; Van Zandt, 156-158
1864
Lost territory Idaho lost to creation of Deer Lodge (Montana), and lost to Missoula (Montana).
to Deer Lodge (Mont.)to Missoula (Mont.)
16 January 1864 · Id. Terr. Laws 1863, loc. and spec., 1st sess., sec. 1/p. 674
1864
Exchanged territory Idaho exchanged with Boise, lost to Nez Perce.
with Boise with Nez Perce
4 February 1864 · Id. Terr. Laws 1863, loc. and spec., 1st. sess., sec. 3/p. 629
1866
Lost territory Idaho lost to Nez Perce.
to Nez Perce
5 January 1866 · Id. Terr. Laws 1865, 3rd. sess., ch. 38/pp. 182-183
1867
Gained territory Idaho gained from Nez Perce.
from Nez Perce
9 January 1867 · Id. Terr. Laws 1866, 4th sess., ch. 48/p. 126
1867
Lost territory Idaho lost to Ada.
to Ada.
10 January 1867 · Id. Terr. Laws 1866, 4th sess., ch. 46/p. 124
1869
Lost territory Idaho lost to creation of Lemhi.
to Lemhi
9 January 1869 · Id. Terr. Laws 1868, 5th sess., ch. 19/pp. 117-118
1873
Lost territory Idaho lost to Ada, Boise, and Lemhi.
to Ada to Boise to Lemhi
10 January 1873 · Id. Terr. Laws 1872, 7th sess., pp. 30-31; 47-48; 64-65
1875
Gained territory Idaho gained from Nez Perce.
from Nez Perce
8 January 1875 · Id. Terr. Laws 1874-1875, comp., rev., 8th sess., pp. 730-732
1879
Gained territory Idaho gained from Ada.
from Ada.
20 February 1879 · Id. Terr. Laws 1879, 10th sess., pp. 40-42
1885
Gained territory Idaho gained from Boise, Lemhi, and Nez Perce.
from Boise from Lemhi from Nez Perce
21 January 1885 · Id. Terr. Laws 1884, 13th sess., p. 126
1887
Exchanged territory Idaho exchanged with Boise.
with Boise
15 January 1887 · Id. Terr. Laws 1887, comp., spec. and loc., 14th sess., p. 120
1887
Boundary clarified Idaho boundaries redefined (no change).
no change
1 June 1887 · Id. Terr. Laws 1887, comp., spec. and loc., 14th sess., p. 133
1889
Lost territory Idaho lost to Custer.
to Custer
4 February 1889 · Id. Terr. Laws 1888, 15th sess., pp. 22-23
1889
Exchanged territory Idaho exchanged with Nez Perce.
with Nez Perce
7 February 1889 · Id. Terr. Laws 1888, 15th sess., pp. 50-51
1890
Became part of Idaho Idaho 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
1891
Exchanged territory Idaho exchanged with Washington.
with Washington
11 February 1891 · Id. Laws 1890, 1st sess., pp. 41-42
1891
Boundary clarified Idaho northern boundary clarified (no change).
no change
2 March 1891 · Id. Laws 1890, 1st sess., pp. 117-118
1895
Lost territory Idaho lost to Washington.
to Washington
23 February 1895 · Id. Laws 1895, 3rd sess., pp. 21-22
1899
Boundary clarified Idaho redefined (no change).
no change
2 February 1899 · Id. Laws 1899, 5th sess., pp. 79-80
1903
Lost territory Idaho lost to Lemhi when line between the two counties was redefined. Faulty geographic knowledge also created an overlap between Idaho and Lemhi (see Overlap Area 2).
to Lemhi
21 February 1903 · Id. Laws 1903, 7th sess., pp. 48-49
1911
Lost territory Idaho lost to Lemhi. Overlap between Idaho and Lemhi (see 21 February 1903) settled in favor of Idaho; Overlap Area 2 eliminated.
to Lemhi
10 March 1911 · Id. Laws 1911, 11th sess., ch. 218/pp. 699-701
1917
Changed Legislature authorized the creation of Selway (proposed) from Idaho and Lewis, dependent on a vote in a special election held 2 July 1917. Proposal failed in referendum (no change).
SelwayLewis
14 March 1917 · Id. Laws 1917, 14th sess., ch. 127/pp. 418-430; www.researchnetwork.net
1918
Lost territory Idaho lost to creation of Valley. Act approved 26 February 1917, became effective through a vote in the general election of 6 November 1918.
to Valley
6 November 1918 · Id. Laws 1917, 14th sess., ch. 99/pp. 360-372
1919
Changed Legislature authorized Valley to annex territory from Idaho, dependent on a vote in the general election of November 1920. No evidence this vote ever took place (no change).
Valley
19 February 1919 · Id. Laws 1919, 15th sess., ch. 101/pp. 366-367; Id. Code Ann. (1996), vol. 6, ch. 1, sec. 31-145 "Valley Co."/pp. 56-57

Land and parcels

What the maps cover in Idaho

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

Parcels Good enough

Lot lines and tax-map numbers for 28,590 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 Official

One point per address, 11,502 in all from State of Idaho ArcGIS Online organization (owner pbond__idaho; Idaho Geospatial Council / Idaho Office of Information Technology Services, 'The Idaho Map').
edited 2 October 2026 · 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

Idaho by the Census

Population

16,541 2020 Census count

Housing units

8,872 2020 Census count

Land area

8,478 square miles

Water area

26 square miles

People per sq mi

2 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.

Records

Assessor and property recordsfrom idahocounty.org · checked 13 October 2026

Permits

Concealed Weapons Permit FAQ – Official Idaho County Sitefrom idahocounty.org

Zoning and code

Ordinancesfrom codelibrary.amlegal.com

County government

County government
The official website of Idaho County.
idahocounty.org

See your own lot on these maps

Open Idaho 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 Idaho County

When was Idaho County founded?: Idaho County was founded in 1861, formed from Shoshone County, and named after Idaho.
What is the county seat of Idaho County?: The county seat of Idaho County is Grangeville.
Is there an online parcel map for Idaho County?: Yes. Idaho Department of Water Resources publishes a parcel map of 28,590 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Idaho County's boundary or name changed?: Idaho County was created in 1861 from Shoshone County. Since then the Atlas of Historical County Boundaries records 21 later changes, chiefly involving Nez Perce County, Boise County and Lemhi County.
Who issues building permits in Idaho County?: The county's page on building permits: Concealed Weapons Permit FAQ – Official Idaho County Site. Inside a city or town, ask that city first.
Is my lot in a flood zone?: We do not have flood maps for Idaho County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby