When was Natrona County founded?

Natrona County was founded in 1888, formed from Carbon County, and named after natron.

What is the county seat of Natrona County?

The county seat of Natrona County is Casper.

Is there an online parcel map for Natrona County?

Yes. A public source publishes a parcel map of 42,891 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Natrona County's boundary or name changed?

Natrona County was created in 1888 from Carbon County. Since then the Atlas of Historical County Boundaries records 5 later changes, chiefly involving Converse County, Carbon County and Fremont County.

Is my lot in a flood zone?

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

County · code 56025

Natrona CountyWyoming

Natrona County is a county in Wyoming with its seat in Casper, formed on March 9, 1888.

Founded1888
County seatCasper
Named fornatron
Land area5,341 sq mi + 35 sq mi water
Population79,955 2020 Census
Parcels mapped42,891 checked 16 October 2026

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

Updated 20 October 2026

Census outline · seat marked

History

Formed in 1888 from Carbon County

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

Natrona County was created from Carbon County by Wyoming Territory in 1888 but was not fully organized, so it was attached to Carbon for administrative and judicial purposes. The county was fully organized and detached from Carbon on April 11, 1890, and became a county in the state of Wyoming on July 10, 1890. Natrona gained territory from Fremont County in 1909, and adjusted boundaries with Johnson and Converse counties in 1911 to run on federal land survey lines.

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

1888
Natrona County created Natrona created by Wyoming Territory from Carbon; Natrona not fully organized, attached to Carbon for administrative and judicial purposes.
from Carbon
9 March 1888 · Wyo. Terr. Laws 1888, 10th leg., ch. 90, sec. 61/pp. 217-218
1890
Changed Natrona fully organized, detached from Carbon.
Carbon
11 April 1890 · Trenholm, 1:331
1890
Became part of Wyoming Natrona became a county in the state of Wyoming. 10 July 1890 · Wyoming Constitution 1889, art. 12 in Swindler, 10:493; U.S. Stat., vol. 26, ch. 664[1890]/pp. 222-226; Van Zandt, 145
1909
Gained territory Natrona gained from Fremont.
from Fremont
27 February 1909 · Wyo. Laws 1909, 10th leg., ch. 129, secs. 2-3/pp. 175-176
1911
Lost territory Natrona lost to Johnson when boundary was adjusted to run on federal land survey lines. Boundary with Converse was adjusted to run on federal land survey lines.
to Johnson to Converse
21 February 1911 · Wyo. Laws 1911, 11th leg., ch. 77, secs. 2, 4, 7, 9/pp. 102-109
1931
Gained territory Natrona gained small areas from Converse in Township 32 North.
from Converse
6 March 1931 · Wyo. Laws 1931, 21st leg., ch. 124/pp. 188-189

Land and parcels

What the maps cover in Natrona

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

Parcels Good enough

Lot lines and tax-map numbers for 42,891 parcels. 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 Natrona 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

Natrona by the Census

Population

79,955 2020 Census count

Housing units

36,808 2020 Census count

Land area

5,341 square miles

Water area

35 square miles

People per sq mi

15 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

Natrona 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 Natrona County.
natronacounty-wy.gov

See your own lot on these maps

Open Natrona 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 Natrona County

When was Natrona County founded?: Natrona County was founded in 1888, formed from Carbon County, and named after natron.
What is the county seat of Natrona County?: The county seat of Natrona County is Casper.
Is there an online parcel map for Natrona County?: Yes. A public source publishes a parcel map of 42,891 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Natrona County's boundary or name changed?: Natrona County was created in 1888 from Carbon County. Since then the Atlas of Historical County Boundaries records 5 later changes, chiefly involving Converse County, Carbon County and Fremont County.
Is my lot in a flood zone?: We do not have flood maps for Natrona County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby