U.S. Census Geocoder and TIGERweb
The public Census Geocoder converts a complete U.S. street address into a matched address and coordinates. ZIP, state, county, city, and Census-designated-place discovery uses official Census TIGERweb center coordinates. Both services are keyless.
Census Geocoder API documentation · Census TIGERweb services
USDA NRCS Soil Data Access / SSURGO
Soil Data Access supplies the SSURGO polygon intersection, map-unit metadata, components, horizons, texture groups, restrictions, monthly flooding and ponding classifications, and aggregated map-unit attributes. Polygon geometry comes from USDA's WFS.
Soil Data Access web-service help · USDA SSURGO overview and downloads
OpenFreeMap and OpenStreetMap
The confirmation map uses OpenFreeMap vector tiles rendered with MapLibre GL JS. Basemap context is separate from USDA soil data and does not determine the soil result.