This directory includes GeoTIFF grids and shapefiles of magnetic data that cover the countries of the US and Canada. GeoTIFF grids of national-scale magnetic anomaly data for the conterminous United States (Ravat and others, 2009), Alaska (Division of Geological and Geophysical Surveys, 2016) and Canada (Miles and Oneschuk, 2016) were merged to create a composite residual magnetic anomaly grid of the United States and Canada. Several derivative products were calculated from the residual magnetic anomaly grid and are provided in this directory. Derivative grids include a reduced-to-pole (RTP) magnetic anomaly grid, the 1st vertical derivative of the RTP, the horizontal gradient magnitude pseudo-gravity calculated from the RTP grid, the long-wavelength RTP magnetic anomaly, and the horizontal gradient magnitude of the long wavelength pseudo gravity calculated from the long wavelength RTP. The directory also includes shapefiles of locations that trace the maxima of the horizontal gradient magnitude of the pseudo-gravity and of the maxima of the horizontal gradient magnitude of the long wavelength RTP transformed to pseudo-gravity. Otherwise known as “worms”, the points tracking the maxima mark the edges of shallow magnetic sources (in the case of the RTP) and deeper magnetic sources (calculated from the long-wavelength RTP grid). The shapefile of worms also includes attribute fields related to the steepness of the gradient and to the trend or strike of the gradient. These products were used in combination with other geophysical and geological data layers as input into a mineral prospectivity model for basin-hosted Pb-Zn mineralization. The reader is encouraged to read the metadata specific to each data layer for details related to the calculation and derivation of each magnetic anomaly GeoTIFF grid or shapefile. References Division of Geological and Geophysical Surveys, 2016, Alaska merged geophysical data grids: Alaska Division of Geological and Geophysical Surveys Digital Data Series 12, https://doi.org/10.14509/29555. Miles, W., and Oneschuk, G., 2016, Magnetic anomaly map, Canada / Carte des anomalies magnetiques, Canada: Geological Survey of Canada Open File 7799, https://doi.org/10.4095/297337. Ravat, D., Finn, C., Hill, P., Kucks, R., Phillips, J., Blakely, R., Bouligand, C., Sabaka, T., Elshayat, A., Aref, A., and Elawadi, E., 2009, A preliminary, full spectrum, magnetic anomaly grid of the United States with improved long wavelengths for studying continental dynamics: A website for distribution of data: U.S. Geological Survey Open-File Report 2009-12258, https://doi.org/10.3133/ofr20091258. [Also available at https://pubs.usgs.gov/of/2009/1258/.]