What is the county seat of Sierra County?

The county seat of Sierra County is Truth or Consequences.

Is there an online parcel map for Sierra County?

Yes. Sierra County publishes a parcel map of 15,959 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Sierra County's boundary or name changed?

Sierra County was created in 1884 from Do County, Ana County, Grant County and Socorro County. Since then the Atlas of Historical County Boundaries records 1 later change, chiefly involving Socorro County.

Is my lot in a flood zone?

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

County · code 35051

Sierra CountyNew Mexico

Sierra County is a county in New Mexico, formed in 1884 and seated in Truth or Consequences.

Founded1884
County seatTruth or Consequences
Named forBlack Range, New Mexico
Land area4,181 sq mi + 57 sq mi water
Population11,576 2020 Census
Parcels mapped15,959 checked 16 October 2026

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

Updated 19 October 2026

Census outline · seat marked

History

Formed in 1884 from Do County, Ana County, Grant County and Socorro County

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

Sierra County was created on April 3, 1884, from parts of Doña Ana, Grant, and Socorro counties. The county was named after the Black Range. In 1950, Sierra County gained additional territory from Socorro County by special election.

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

1884
Sierra County created Sierra created by New Mexico Territory from DoÑA Ana, Grant, and Socorro.
from Do from Anafrom Grantfrom Socorro
3 April 1884 · N.M. Terr. Laws 1884, 26th assy, ch. 109/pp. 223-225
1909
Changed Territorial Legislature authorized Sierra to gain from Socorro in "An Act to abolish the county of Sierra.... And creating a new county with different boundaries with the name of Sierra." Change was not approved by the U.S. Congress, as required by The Organic Act for the Territory of New Mexico (1850) (no change).
SocorroU.s.
17 March 1909 · N.M. Terr. Laws 1909, 38th assy., ch. 61/pp. 160-166; U.S. Stat., vol. 9, ch. 49[1850], sec. 7/p. 449; Coan, p. 19
1917
Boundary clarified Boundary between Sierra and Grant redefined to run on the line between Township 12S and Township 13S (no change).
with Grantno change
12 March 1917 · N.M. Laws 1917, 3rd reg. sess., ch. 57/pp. 178-179
1950
Gained territory Sierra gained from Socorro by a special election.
from Socorro
7 March 1950 · N.M. Compiled Stat. 1999, ch. 4, article 27, sec. 1/p. 43; election certificate filed with the Sierra County Clerk on 13 September 1951

Land and parcels

What the maps cover in Sierra

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

Parcels Good enough

Lot lines and tax-map numbers for 15,959 parcels from Sierra County. 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 Sierra 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

Sierra by the Census

Population

11,576 2020 Census count

Housing units

8,056 2020 Census count

Land area

4,181 square miles

Water area

57 square miles

People per sq mi

3 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

Sierra 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 Sierra County.
sierracountynm.gov

See your own lot on these maps

Open Sierra 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 Sierra County

When was Sierra County founded?: Sierra County was founded in 1884, formed from Do County, Ana County, Grant County and Socorro County, and named after Black Range, New Mexico.
What is the county seat of Sierra County?: The county seat of Sierra County is Truth or Consequences.
Is there an online parcel map for Sierra County?: Yes. Sierra County publishes a parcel map of 15,959 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Sierra County's boundary or name changed?: Sierra County was created in 1884 from Do County, Ana County, Grant County and Socorro County. Since then the Atlas of Historical County Boundaries records 1 later change, chiefly involving Socorro County.
Is my lot in a flood zone?: We do not have flood maps for Sierra 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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