Soil Maps of the United States of America

National soil maps provide an important archive depicting soil science theory and ideas behind the application of soils information at the time the maps were created. A look at soil maps of the USA produced since the beginning of the twentieth century shows a move from a geologic‐based concept of soils to a pedologic concept of soils. These maps also show changes from property‐based systems to process‐based, and then back to property‐based, and ideas on diagnostic mapping of soil properties changed over time. The national soil mapping program in the USA was established in 1899. The earliest nation‐wide soil map was published by M. Whitney in 1909 consisting of soil provinces that were largely based on geology. In 1912 G.N. Coffey published the first country‐wide map based on soil properties; the map showed 22 soil units belonging to 5 divisions based on parent material, color, and drainage. The next national map was produced by C.F. Marbut, H.H. Bennett, J.E. Lapham, and M.H. Lapham in 1913 and showed 13 broad physiographic units that were further subdivided into soil series, soil classes and soil types. In 1935 Marbut drafted a series of maps based on soil properties, but these maps were replaced as official U.S. soil maps in 1938 with the work of M. Baldwin, C.E. Kellogg, and J. Thorp. Modern soil maps appeared in the 1960s with the seventh Approximation and followed with the 1975 and 1999 editions of Agriculture Handbook number 436, Soil Taxonomy.