County · code 05139
Union CountyArkansas
Union County is a county in Arkansas, formed in 1829 with El Dorado as its county seat.
- Founded1829
- County seatEl Dorado
- Land area1,039 sq mi + 16 sq mi water
- Population39,054 2020 Census
- Parcels mapped31,636 checked 14 October 2026
Where it is
Union on the map of Arkansas
Arkansas has 75 counties and county equivalents, each with its own records office. Shapes with a page are links.
History
Formed in 1829 from Clark County and Hempstead County
An old deed may name a county that no longer exists, or a boundary that has since moved.
Union County was created on November 2, 1829, by Arkansas Territory from Clark, Hempstead, and Non-County Area 2. The county gained territory from Chicot in 1835 and became a county in the state of Arkansas on June 15, 1836. Over the following decades, Union County lost land to the creation of Bradley, Ouachita, Calhoun, and Columbia Counties, and to transfers to Lafayette and other counties.
- 1829Union County created Union created by Arkansas Territory from Clark, Hempstead, and Non-County Area 2. · Ark. Terr. Acts 1829, 6th sess., pp. 51-54
- 1835
- 1836Became part of Arkansas Union became a county in the state of Arkansas. · U.S. Stat., vol. 5, chs. 100, 120 [1836]/pp. 50-52, 58-59; Swindler, 1: 342-344, 354-358; Van Zandt, 119
- 1840
- 1842Lost territory Union lost to creation of Ouachita. · Ark. Acts 1842, 4th sess., pp. 11-14
Show all 12 changes
- 1829Union County created Union created by Arkansas Territory from Clark, Hempstead, and Non-County Area 2. · Ark. Terr. Acts 1829, 6th sess., pp. 51-54
- 1835
- 1836Became part of Arkansas Union became a county in the state of Arkansas. · U.S. Stat., vol. 5, chs. 100, 120 [1836]/pp. 50-52, 58-59; Swindler, 1: 342-344, 354-358; Van Zandt, 119
- 1836Gained territory Union gained small area from Pulaski, exchanged with Jefferson, lost to Clark. · Ark. Acts 1836, 1st sess., pp. 126-127, 161, 186
- 1840
- 1842Lost territory Union lost to creation of Ouachita. · Ark. Acts 1842, 4th sess., pp. 11-14
- 1846
- 1850Lost territory Union lost to creation of Calhoun. · Ark. Acts 1850, 8th sess., pp. 28-32; Ark. Acts 1852, 9th sess., pp. 34-35
- 1852Lost territory Union lost to creation of Columbia. · Ark. Acts 1852, 9th sess., pp. 29-34
- 1853
- 1858
- 1862Gained territory Union gained small area from Calhoun along the Ouachita River in townships 17 and 18 when the boundary was moved from the high water mark on the west side of the river to the center of the channel. · Ark. Acts 1862, 14th sess., p. 6
Land and parcels
What the maps cover in Union
Who publishes each layer, how good it is, and when we last checked.
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Parcels Good enough
Lot lines and tax-map numbers for 31,636 parcels from Arkansas GIS Office. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
checked 14 October 2026 -
Address points Official
One point per address, 23,904 in all from Arkansas GIS Office (state GIS office).
checked 13 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
Union by the Census
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.
Records
County government
- County government
The official website of Union County.
See your own lot on these maps
Open Union 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.
Questions
Common questions about Union County
- When was Union County founded?
- Union County was founded in 1829, formed from Clark County and Hempstead County.
- What is the county seat of Union County?
- The county seat of Union County is El Dorado.
- Is there an online parcel map for Union County?
- Yes. Arkansas GIS Office publishes a parcel map of 31,636 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
- Has Union County's boundary or name changed?
- Union County was created in 1829 from Clark County and Hempstead County. Since then the Atlas of Historical County Boundaries records 11 later changes, chiefly involving Calhoun County, Columbia County and Ouachita County.
- Is my lot in a flood zone?
- We do not have flood maps for Union County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.
Nearby