Union County, South Dakota GIS Map
This GIS map of Union County, South Dakota (SD) shows the official Census county boundary (FIPS 46127), with federal layers you can switch on for FEMA flood zones, USGS elevation contours and hillshade, NLCD land cover, and school district lines.
Union County has a population of about 17,081 (U.S. Census Bureau, 2020-2024 ACS 5-year estimate) and a land area of 460.8 square miles. Use the inspect tool to read coordinates, elevation and the layers under any point.
- State
- South Dakota (SD)
- Population
- 17,081
- Land area
- 460.8 sq mi
- Density
- 37 / sq mi
- Coordinates
- 42.8311, -96.6508
- FIPS code
- 46127
Union County is not the only one — there are 17 other states with a county of the same name. Compare every Union County.
Union County Demographics
Source: U.S. Census Bureau, American Community Survey 2020-2024 5-year estimates.
Population
17,081
Households
7,310
Median household income
$89,636
Median age
41.5 years
Median home value
$301,100
Median gross rent
$1,069/mo
Owner-occupied homes
73.1%
Bachelor's degree or higher
37%
Below poverty level
6.2%
Land area
460.8 sq mi
Population density
37 / sq mi
Union County Population Growth
Source: U.S. Census Bureau, 2010 Census and Population Estimates Program (Vintage 2024: April 2020 estimates base and July 1, 2024 estimate).
2010 Census
14,399
April 2020 (estimates base)
16,814
July 2024 estimate
17,402
Change 2010-2020
+16.8%
Change 2020-2024
+3.5%
Natural Hazard Risk in Union County
FEMA National Risk Index ratings for Union County, compared with all U.S. counties.
Overall risk
Score 37.1 of 100
Expected annual loss
Buildings, population & agriculture
Social vulnerability
Susceptibility to hazard impacts
Community resilience
Ability to prepare & recover
Risk by Hazard
- WildfireRelatively Low
- Winter WeatherRelatively Moderate
- DroughtRelatively Moderate
- HailRelatively Moderate
- TornadoRelatively Moderate
- Ice StormRelatively Moderate
- Inland FloodingRelatively Low
- LandslideVery Low
- Cold WaveRelatively Low
- Heat WaveVery Low
- LightningRelatively Low
- Strong WindRelatively Low
- EarthquakeVery Low
Source: FEMA National Risk Index (December 2025 release). County-level ratings are relative to other U.S. counties and are not a property-specific assessment.
Environmental Conditions in Union County, South Dakota
Radon potential, monitored air quality and current drought status for Union County, South Dakota, from the Environmental Protection Agency and the U.S. Drought Monitor.
Radon potential
Zone 1
highest radon potential
EPA predicts an average indoor level at or above 4 pCi/L, so the EPA recommends a radon test for every home in this zone, and a mitigation system for new construction.
Drought status
Moderate drought in 1.2% of the county
Drought Severity and Coverage Index 38.3 of 500.
- D0 Abnormally dry35.8%
- D1 Moderate drought1.2%
Map of 13 October 2026.
Sources: EPA Map of Radon Zones (September 2025), EPA Air Quality Index (2024) and the U.S. Drought Monitor. A radon zone is a regional planning tool, not a prediction for any individual home — the EPA recommends testing every home regardless of zone. Air quality is shown only for counties that host an EPA monitor. Drought figures describe one weekly map, not a long-term climate average. Compare counties in South Dakota.
GIS Data for Union County, SD
The Union County GIS map on this page loads live federal layers in your browser, so you can check flood zones, terrain, land cover and district boundaries anywhere in Union County without a separate GIS login. All of the Union GIS data below is drawn from public U.S. government sources.
Layers you can turn on
FEMA flood zones
National Flood Hazard Layer — flood insurance rate map zones and floodways.
Elevation contours and hillshade
USGS 3DEP terrain, so you can read slope and relief across the county.
Land cover
NLCD land cover classes — forest, developed, wetland and water.
School districts
Census TIGER unified and elementary school district boundaries.
ZIP code and county boundaries
Census TIGER ZCTA and county boundary lines.
Map tools
Measure distance and area
Draw a line or polygon to get length in miles or area in acres.
Sketch and annotate
Add points, lines and shapes on top of the map.
Inspect any point
Click the map to read coordinates, elevation and the layers under your cursor.
Download the map
Save the current view as a PNG image.
Where the data comes from
County boundaries come from the U.S. Census Bureau TIGER/Line program, flood zones from FEMA's National Flood Hazard Layer, terrain from the USGS 3D Elevation Program, land cover from the Multi-Resolution Land Characteristics Consortium, and demographics from the American Community Survey.
Property records and tax maps in Union County
Most people who look up Union County GIS data are after parcel-level records: who owns a property, what it last sold for, and what it is assessed at. Those records are kept locally, not federally, so they are not part of this map. Union County property and tax map data lives with the county's own records office, and what that office is called varies by state — Texas counties run an appraisal district (usually searched as a “CAD”), Kentucky uses a Property Valuation Administrator (PVA), and most other states use a county assessor, auditor or tax office. Start with that office for a deed, a tax map number or a parcel boundary; use the map above for flood zones, elevation and land cover on the same land.
Union County FAQ
What state is Union County in?
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Union County is a county in South Dakota (SD).
What is the population of Union County?
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Union County, South Dakota has a population of about 17,081, according to the U.S. Census Bureau American Community Survey.
How big is Union County?
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Union County covers about 460.8 square miles of land, with a population density of roughly 37 people per square mile.
What is the FIPS code for Union County?
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The FIPS county code for Union County, South Dakota is 46127. It is used to identify the county in federal datasets such as Census TIGER and FEMA flood maps.
What is the median household income in Union County?
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The median household income in Union County, South Dakota is about $89,636 per year.
What is the radon zone for Union County?
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Union County is in EPA radon Zone 1, meaning the EPA predicts an average indoor radon level at or above 4 pCi/L. In this zone the EPA recommends a radon test for every home in this zone, and a mitigation system for new construction. The EPA is clear that a radon zone is a regional planning tool and not a prediction for any individual home.
Is Union County in a drought?
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As of the 13 October 2026 U.S. Drought Monitor map, moderate drought covers 1.2% of Union County, and the county's Drought Severity and Coverage Index is 38.3 out of 500.
What is Union GIS?
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Union GIS usually refers to the county's own parcel and zoning mapping system, which Union County publishes itself. This page is a separate, free viewer: it draws federal GIS layers — FEMA flood zones, USGS elevation, NLCD land cover and Census boundaries — over the Union County boundary, with no login required.
What GIS data is available for Union County?
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The Union County map loads federal GIS layers directly in your browser: FEMA National Flood Hazard Layer flood zones, USGS 3DEP elevation contours and hillshade, NLCD land cover, Census TIGER school district boundaries, and TIGER ZIP code and county boundary lines.
How do I check flood zones in Union County?
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Open the Union County map, turn on the FEMA flood zones layer, and zoom in. The National Flood Hazard Layer shows flood insurance rate map zones and floodways. Flood zones only draw once you are zoomed in far enough.
How do I find the coordinates or elevation of a spot in Union County?
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Use the inspect tool on the Union County map and click any point. It reads back the coordinates, elevation and the layers under your cursor. You can also measure distance and area by drawing a line or polygon.
Data sources for Union County, South Dakota
Every figure on this page comes from a published government dataset. Each source is listed with its release date so you can check the number or cite it directly.
- American Community Survey 5-year estimates
U.S. Census Bureau · 2020-2024 · population, income, housing, education and poverty figures
- Gazetteer Files
U.S. Census Bureau · 2024 · place coordinates, land area and the county/place/ZIP crosswalk
- TIGER/Line Shapefiles
U.S. Census Bureau · 2024 · county, ZIP Code Tabulation Area and school district boundaries
- National Flood Hazard Layer
Federal Emergency Management Agency · current effective Flood Insurance Rate Maps · flood zones, floodways and base flood elevations
- National Risk Index
Federal Emergency Management Agency · v1.20, December 2025 · county natural hazard risk, expected annual loss, social vulnerability and resilience
- 3D Elevation Program (3DEP)
U.S. Geological Survey · current · elevation contours, shaded relief and point elevations
- National Land Cover Database
Multi-Resolution Land Characteristics Consortium · NLCD 2021 · land cover classes such as developed, forest, crop and water
- Map of Radon Zones
U.S. Environmental Protection Agency · September 2025 · the county radon zone (1, 2 or 3) and its predicted indoor radon potential
- Air Quality Index annual summary by county
U.S. Environmental Protection Agency · 2024 · median, 90th percentile and peak AQI, and days at unhealthy levels, for counties with an EPA monitor
- U.S. Drought Monitor
National Drought Mitigation Center, USDA and NOAA · weekly, current map · the share of county area in each drought category and the Drought Severity and Coverage Index
- ArcGIS basemaps
Esri · current · streets, satellite, topographic and dark gray basemap tiles
Citing this page
GIS Map, “Union County, South Dakota GIS Map”, https://gismap.land/county/south-dakota/union. Figures from the datasets listed above.
Local notes for Union County, SD
Questions and local knowledge from people who know the area. Every note is read before it appears here.