A digital magnetic anomaly database and map for the NorthAmerican continent is the result of a joint effort by theGeological Survey of Canada (GSC), U. S. Geological Survey(USGS), and Consejo de Recursos Minerales of Mexico (CRM). Thedatabase and map represent a substantial upgrade from theprevious compilation of magnetic anomaly data for NorthAmerica, now over a decade old.This report presents three unique, gridded data sets used tomake the magnetic anomaly map of North America. All threegrids have 1-km spacing and are projected to the DNAGprojection. These grids are provided in Geosoft binary gridformat, with two files describing each of the grids (suffixes.grd and .gi).The first grids (NAmag_origmrg.grd and USmag_origmrg.grd) showthe magnetic field at 1,000 m. above terrain.For the second grids (NAmag_hp500.grd and USmag_hp500.grd) weremoved long-wavelength anomalies (500 km and greater) from thefirst grid. This grid was used for the published map.Although the North American merged grid represents asignificant upgrade to older compilations, the existingpatchwork of surveys is inherently unable to accuratelyrepresent anomalies with long (greater than roughly 150 km)wavelengths, particularly in the US and Canada (U.S. Magnetic-Anomaly Data Set Task Group, 1994). The lack of informationabout long wavelength anomalies is primarily related to datumshifts between merged surveys, caused by data acquisition atwidely different times and by differences in mergingprocedures. Therefore, we removed anomalies with wavelengthsgreater than 500 km from the merged grid to reduce the effectscaused by the spurious long wavelengths but still maintain thecontinuity of anomalies. The correction was accomplished bytransforming the merged grid to the frequency domain, filteringthe transformed data with a long-wavelength cutoff at 500 km,and subtracting the long-wavelength data grid from the mergedgrid.In addition to the 500-km high pass filter, an equivalentsource method, based on long-wavelength characterization usingsatellite data (CHAMP satellite anomalies, Maus and others,2002), was also used to correct for spurious shifts in theoriginal magnetic anomaly grid (Ravat and others, 2002). Theseresults are presented in the third grids (NAmag_CM.grd andUSmag_CM.grd), in which the wavelengths longer than 500 km havebeen replaced by downward-continued satellite data.