Classes of land-surface form in the United States

This digital dataset describes classes of land-surface form in
the conterminous United States. The source of the data is the
map of land-surface form in the 1970 National Atlas of the
United States, pages 62-63, which was adapted from Edwin
H. Hammond, "Classes of land surface form in the forty-eight
states, U.S.A," Annals of the Assoc. of Am. Geographers, v.54,
no. 1, 1964, map supp. no. 1, 1:5,000,000.