When was Cassia County founded?

Cassia County was founded in 1879, formed from Oneida County and Owyhee County, and named after Cassia Creek, Idaho.

What is the county seat of Cassia County?

The county seat of Cassia County is Burley.

Is there an online parcel map for Cassia County?

Yes. Idaho Department of Water Resources publishes a parcel map of 19,575 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Cassia County's boundary or name changed?

Cassia County was created in 1879 from Oneida County and Owyhee County. Since then the Atlas of Historical County Boundaries records 3 later changes, chiefly involving Power County and Twin Falls County.

Is my lot in a flood zone?

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

County · code 16031

Cassia CountyIdaho

Cassia County is in Idaho with its county seat in Burley. The county was formed on February 20, 1879.

Founded1879
County seatBurley
Named forCassia Creek, Idaho
Land area2,566 sq mi + 15 sq mi water
Population24,655 2020 Census
Parcels mapped19,575 checked 16 October 2026

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

Updated 20 October 2026

Census outline · seat marked

History

Formed in 1879 from Oneida County and Owyhee County

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

Cassia County was created by Idaho Territory from Oneida and Owyhee counties and named after Cassia Creek. When Idaho became a state in 1890, Cassia County continued as an Idaho county. The county lost land in 1907 when Twin Falls County was created, and again in 1913 when Power County was created.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries.

1879
Cassia County created Cassia created by Idaho Territory from Oneida and Owyhee.
from Oneida from Owyhee
20 February 1879 · Id. Terr. Laws 1879, 10th sess., pp. 43-46
1881
Boundary clarified Eastern line of Cassia clarified (no change).
no change
9 February 1881 · Id. Terr. Laws 1880, 11th sess., p. 339
1887
Boundary clarified Cassia boundaries redefined (no change).
no change
1 June 1887 · Id. Terr. Laws 1887, comp., spec. and loc., 14th sess., p. 125
1890
Became part of Idaho Cassia 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
1907
Lost territory Cassia lost to creation of Twin Falls.
to Twin Falls
21 February 1907 · Id. Laws 1907, 9th sess., pp. 40-41
1913
Lost territory Cassia lost to creation of Power.
to Power
30 January 1913 · Id. Laws 1913, 12th sess., ch. 6/pp. 30-45

Land and parcels

What the maps cover in Cassia

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

Parcels Good enough

Lot lines and tax-map numbers for 19,575 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 Cassia 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

Cassia by the Census

Population

24,655 2020 Census count

Housing units

8,838 2020 Census count

Land area

2,566 square miles

Water area

15 square miles

People per sq mi

10 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

Cassia 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 Cassia County.
cassiacounty.org

See your own lot on these maps

Open Cassia 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 Cassia County

When was Cassia County founded?: Cassia County was founded in 1879, formed from Oneida County and Owyhee County, and named after Cassia Creek, Idaho.
What is the county seat of Cassia County?: The county seat of Cassia County is Burley.
Is there an online parcel map for Cassia County?: Yes. Idaho Department of Water Resources publishes a parcel map of 19,575 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Cassia County's boundary or name changed?: Cassia County was created in 1879 from Oneida County and Owyhee County. Since then the Atlas of Historical County Boundaries records 3 later changes, chiefly involving Power County and Twin Falls County.
Is my lot in a flood zone?: We do not have flood maps for Cassia County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby