This line shapefile represents the major fault lines in the United States. A fault is a fracture or fracture zone in the Earth's crust along which rocks on one side have moved significantly with respect to those on the other side. This layer is part of the Geologic Map of the United States, originally published at a scale of 1:2,500,000 (King and Beikman, 1974b). It excludes Alaska and Hawaii. These data depict the geology of the bedrock that lies at or near the land surface, but not the distribution of surficial materials such as soils, alluvium, and glacial deposits. This is a revised version of the April 2004 data set. This map complements the Generalized Geologic Map of Alaska, Hawaii, Puerto Rico, and the U.S. Virgin Islands by Reed and Bush. This layer is part of the 1997-2014 edition National Atlas of the United States.Conversion of the geologic map of the U.S. to a digital format was undertaken to facilitate the presentation and analysis of earth-science data. Digital maps can be displayed at any scale or projection, whereas a paper map has a fixed scale and projection. However, these data are not intended to be used at any scale finer than 1:2,500,000.