In order to prepare a soil map of the world as requested by the IUSS in 1968,  FAO developed a supra-national legend which has been used as an international soil classification system. Many of the names offered in that classification are known in many countries and do have similar meaning. The FAO/UNESCO legend is a very simple classification system with very broad units, but was the first truly international system, and most soils could be accommodated on the basis of their field descriptions. The FAO soil map was intended for mapping soils at a continental scale but not at local scale.

A major revision of the system was published in 1988. This system was finally replaced by the World Reference Base for Soil Resources in 1998. Many legacy soil reports and maps used this system.