When was Boise County founded?

Boise County was founded in 1863, formed from Idaho County, and named after Boise River, Idaho.

What is the county seat of Boise County?

The county seat of Boise County is Idaho City.

Is there an online parcel map for Boise County?

Not that we have found yet. Lot lines and owners of record are kept by the county assessor's office. When a public parcel map appears, it shows here.

Has Boise County's boundary or name changed?

Boise County was created in 1863 from Idaho County. Since then the Atlas of Historical County Boundaries records 18 later changes, chiefly involving Alturas County, Idaho County and Ada. County.

Is my lot in a flood zone?

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

County · code 16015

Boise CountyIdaho

Boise County is a county in Idaho, with its seat in Idaho City. It was created on January 12, 1863, from Idaho County by Washington Territory.

Founded1863
County seatIdaho City
Named forBoise River, Idaho
Land area1,900 sq mi + 7.4 sq mi water
Population7,610 2020 Census

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

Updated 20 October 2026

Census outline · seat marked

History

Formed in 1863 from Idaho County

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

Boise County was named after the Boise River. When Idaho Territory was created on March 3, 1863, Boise County transferred from Washington Territory to Idaho Territory. The county lost most of its territory through the creation of Owyhee County in December 1863 and Oneida County in January 1864. When Idaho became a state in 1890, Boise County continued as an Idaho county.

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

1863
Boise County created Boise created by Washington Territory from Idaho; included parts of present Idaho and Wyoming.
from Idaho
12 January 1863 · Wash. Terr. Laws 1862, 10th sess., pp. 3-4
1863
Became part of Idaho Boise 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
1863
Lost territory Boise lost to creation of Owyhee.
to Owyhee
31 December 1863 · Id. Terr. Laws 1863, loc. and spec., 1st sess., p. 624
1864
Lost territory Boise lost to creation of Oneida.
to Oneida
22 January 1864 · Id. Terr. Laws 1863, loc. and spec., 1st sess., p. 625
1890
Became part of Idaho Boise 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 19 changes (14 more)

1863
Boise County created Boise created by Washington Territory from Idaho; included parts of present Idaho and Wyoming.
from Idaho
12 January 1863 · Wash. Terr. Laws 1862, 10th sess., pp. 3-4
1863
Became part of Idaho Boise 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
1863
Lost territory Boise lost to creation of Owyhee.
to Owyhee
31 December 1863 · Id. Terr. Laws 1863, loc. and spec., 1st sess., p. 624
1864
Lost territory Boise lost to creation of Oneida.
to Oneida
22 January 1864 · Id. Terr. Laws 1863, loc. and spec., 1st sess., p. 625
1864
Exchanged territory Boise exchanged with Idaho; lost to creation of Alturas (extinct).
with Idahowith Alturas
4 February 1864 · Id. Terr. Laws 1863, loc. and spec., 1st. sess., sec. 4/p. 629
1864
Lost territory Boise lost to creation of Ada.
to Ada.
22 December 1864 · Id. Terr. Laws 1864, 2nd sess., ch. 29/pp. 430-431
1866
Exchanged territory Boise exchanged with Alturas (extinct).
with Alturas
12 January 1866 · Id. Terr. Laws 1865, 3rd. sess., ch. 56/p. 214
1867
Lost territory Boise lost to Ada.
to Ada.
10 January 1867 · Id. Terr. Laws 1866, 4th sess., ch. 46/p. 124
1873
Gained territory Boise gained from Idaho.
from Idaho
10 January 1873 · Id. Terr. Laws 1872, 7th sess., pp. 64-65
1879
Lost territory Boise lost to creation of Washington.
to Washington
20 February 1879 · Id. Terr. Laws 1879, 10th sess., pp. 40-42
1881
Gained territory Boise gained a small area (along modern Boise / Custer line) from Alturas (extinct), lost to creation of Custer.
from Custerfrom Alturas
1 April 1881 · Id. Terr. Laws 1880, 11th sess., pp. 340-345
1883
Lost territory Boise lost to Ada and Washington.
to Ada to Washington
31 January 1883 · Id. Terr. Laws 1882, 12th sess., pp. 67-68
1885
Lost territory Boise lost to Idaho.
to Idaho
21 January 1885 · Id. Terr. Laws 1884, 13th sess., p. 126
1887
Gained territory Boise gained from Alturas (extinct), and exchanged with Idaho.
from Alturasfrom Idaho
15 January 1887 · Id. Terr. Laws 1887, comp., spec. and loc., 14th sess., p. 120
1890
Became part of Idaho Boise 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
Lost territory Boise lost to creation of Alta (extinct).
to Alta
3 March 1891 · Id. Laws 1890, 1st sess., pp. 120-124
1891
Gained territory Boise gained from Alta (extinct) when the Idaho Supreme Court declared the act creating Alta unconstitutional because it failed to provide for an election.
from Alta
6 May 1891 · Id. Rpts. 1893, vol. 2/pp. 813-839; Id. Encyclopedia, p. 232
1915
Lost territory Boise lost to creation of Gem. Act approved 19 March 1915, became effective through a vote in the general election of 11 May 1915.
to Gem.
11 May 1915 · Id. Laws 1915, 13th sess., ch. 165/pp. 362-375; Id. Code Ann. (1996), vol. 6, ch. 1, sec. 31-125 "Gem Co."/p. 35
1918
Lost territory Boise lost to creation of Valley. Act approved 26 Feb 1917, became effective through a vote in the general election of November 1918.
to Valley
6 November 1918 · Id. Laws 1917, 14th sess., ch. 99/pp. 360-372

Land and parcels

What the maps cover in Boise

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

Parcels Missing

No public parcel map found for Boise County yet. Lot lines and owners of record are kept by the county (boisecounty.us).
Address points Missing

No public address points layer found for Boise 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

Boise by the Census

Population

7,610 2020 Census count

Housing units

5,443 2020 Census count

Land area

1,900 square miles

Water area

7.4 square miles

People per sq mi

4 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

Boise 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 Boise County.
boisecounty.us

See your own lot on these maps

Open Boise 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 Boise County

When was Boise County founded?: Boise County was founded in 1863, formed from Idaho County, and named after Boise River, Idaho.
What is the county seat of Boise County?: The county seat of Boise County is Idaho City.
Is there an online parcel map for Boise County?: Not that we have found yet. Lot lines and owners of record are kept by the county assessor's office. When a public parcel map appears, it shows here.
Has Boise County's boundary or name changed?: Boise County was created in 1863 from Idaho County. Since then the Atlas of Historical County Boundaries records 18 later changes, chiefly involving Alturas County, Idaho County and Ada. County.
Is my lot in a flood zone?: We do not have flood maps for Boise 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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