Soil scientists have developed a number of systems for identifying and classifying soils. Some broad systems of soil classification are used worldwide, and one of the most widely applied is that developed by the U.S. Department of Agriculture. It includes 11 major soil orders: alfisols, andisols, aridisols, entisols, histosols, inceptisols, mollisols, oxisols, spodisols, ultisols, and vertisols. Each major order is subdivided into suborders, groups, subgroups, families, and series.
Soils are also classified at an extremely specific level: soils are named after a local landmark such as a town, school, church, or stream near where the soil is first identified. There are soils named Amarillo and Fargo, for example, identifying their origins in northwestern Texas and North Dakota, respectively. Soils that share characteristics that fall within defined limits share the same name, and these soils form a soil series. (Local names for soil series are usually used within countries but not across boundaries, even though soils on different continents share the same characteristics.)