This document describes the Landtype Associations that have been developed for National Forest land in the Northern Region. Map units were delineated at a scale of 1:100,000 and are differentiated by dominant categories of landforms and geologic materials. Descriptions of the seventy one Landtype Associations were prepared for the nineteen Sections that occur in Region 1 using the National Hierarchy of Ecological Units. A total of 40,392,207 acres were mapped. Examples of applications using landtype associations are also presented. These landtype associations were developed primarily for use in landscape and watershed characterization. A geo-referenced, electronic version of the mapping was prepared as a component of this mapping project.