This point shapefile contains the locations and attributes of significant, historic earthquakes that caused deaths, property damage, and geological effects, or were otherwise experienced by populations in the United States, Puerto Rico, and U.S. Virgin Islands. Included are earthquakes located in the United States as well as some that occurred in adjacent portions of Canada and Mexico. The main sources for the data are Seismicity of the United States, 1568-1989 and the Preliminary Determination of Epicenters for 1990 to January 2004. This is a replacement for the June 1999 map layer. This layer is part of the 1997-2014 edition National Atlas of the United States. These data are intended for geographic display and analysis at the national level, and for large regional areas. The data should be displayed and analyzed at scales appropriate for 1:2,000,000-scale data. No responsibility is assumed by the National Atlas of the United States or the U.S. Geological Survey in the use of these data. This map layer is intended for a mixed audience of specialists and non-specialists alike who have a need for general, non-technical information about significant United States earthquakes. National Atlas of the United States. (2005). Significant United States Earthquakes, 1568-2009. National Atlas of the United States. Available at: http://purl.stanford.edu/sy174vb2193. Provided with the downloadable files is a text file, quksigx_references.txt, which contains the reference information for earthquake magnitudes listed in the data.