The National Map Download Client from the USGS provides grids (aka rasters) and vector files to use in other software.
The GeoTIFF and IMG formats are recognized by Surfer as valid grid files. You can use them in any place in Surfer that requires a grid file (e.g. creating maps, layers, or for use any of the grid functions under the Grid menu).
The Shapefile and FileGDB formats are recognized by Surfer as valid vector files. These can be used to create base maps.
Updated October 11, 2021