How this site works

The data

The Soil Survey Geographic Database (SSURGO) is the detailed soil map of the United States made by the USDA Natural Resources Conservation Service (NRCS) and its partners. It divides land into map units, each made of one or more soil components (usually named soil series, sometimes land types such as urban land or rock outcrop) with a percentage, and records properties and ratings for each component and its layers (horizons).

We query it through Soil Data Access, NRCS's public SQL service. SSURGO is public domain. This build used 3,386 soil survey areas, retrieved November 3, 2026; the most recent survey area update in it is October 26, 2026. NRCS publishes a refreshed SSURGO each October, and this site re-runs its data build each year after that.

County populations (used only to decide which counties get a full report first) are U.S. Census Bureau county population estimates, Vintage 2024 (Connecticut: Vintage 2020, historical counties).

How shares are calculated

• Area weighting. A soil component's acres in a county = the map unit's acres inside that county (SSURGO's county overlap table) × the component's percentage. Every share is a share of mapped land, so a soil covering 20% of the county counts four times as much as one covering 5%.
• Open water (components named Water) is left out of every denominator.
• Drainage class and hydrologic group are the component values.
• Septic absorption fields use the NRCS interpretation “ENG - Septic Tank Absorption Fields” (overall rating: not limited, somewhat limited, very limited, or not rated).
• Flooding is the most frequent flooding class in any month for each component. Seasonal high water table is the shallowest depth to a wet (saturated) layer in any month; components with monthly records but no wet layer count as “deeper or none”.
• Topsoil is the first mineral horizon starting in the top 30 cm (12 in), skipping leaf litter layers. pH is the representative 1:1 water pH. The “typical” value is the area-weighted median; the range is the 10th to 90th percentile of land.
• Texture groups: organic = muck or peat; clayey = 40% clay or more; sandy = 70% sand or more with under 15% clay; otherwise loamy.
• State comparisons pool all mapped land in the state. They are not an average of county figures.
• Anything missing is shown as “Not rated” or “Not reported”, never as zero.

Soil series pages

A series page combines every SSURGO component with that series name (component kind “Series”). Taxadjuncts and variants are not included. The profile diagram shows the layers of the single largest component of that series by mapped acres, with its representative values; other mapped areas of the same series vary within the series range. The Official Soil Series Descriptions give the full narrative definition of each series.

Pages exist for the 500 series with the most mapped acres.

The ZIP lookup

ZIP codes are matched to counties with the Census Bureau's ZIP Code Tabulation Areas (ZCTAs) and the 2020 ZCTA-to-county relationship file. A ZIP that crosses county lines shows the county holding most of its land, and names the others. The result describes the whole county, not the soil at a specific address.

Full county reports start with the 500 most populous counties that have soil ratings on at least 50% of their mapped land; every other county with data is still available in the lookup.

How the “what this means” notes are written

The garden, lawn and septic notes are filled in from the numbers with fixed thresholds (for example, “soggy spring soil is common” appears when 40% or more of the land is somewhat poorly to very poorly drained; lime advice depends on the typical pH band). They are general guidance for typical conditions, not advice for a specific property.

Photo credits

Photographs are licensed stock images used for illustration only. They do not show the soils or places described on this site.

• Photo: Depositphotos, asset page, standard license.
• Photo: Shutterstock, asset page, standard license.