This original “national” USA soil classification system - Keys to Soil Taxonomy, Twelfth Edition (2014) - has found widespread international acceptance particularly in countries in Latin America and Asia. The principles that were developed by Soil Taxonomy were taken up by WRB and the FAO Legend to set international standards.

This system was first published in 1975, and has undergone several revisions since. It is a hierarchical classification that tries to group similar soils into increasingly general categories. It was designed to support soil survey in the USA, specifically the correlation of soil series and the provision of map unit names at various levels of cartographic detail. It tries to classify all World soils, but the main aim has always been to group soils of the USA.