From February 12 to March 8, 1981, EG and G Geometrics conducted an aeromagnetic survey in Montana for Anaconda Copper Company. A Piper Navajo aircraft was used to conducted the survey. The survey was flown along north-south flightlines spaced 660 feet at a nominal height of 450 feet above the terrain. Five uniformly spaced east-west tie-lines were also flown. During processing, the International Geomagnetic Reference Field (IGRF) of 1975 was updated to 1981 and removed from the survey observations. The resultant anomalous magnetic field was contoured at a 4.0 gamma interval and plotted to map sheets. In 2016, the map sheets were scanned, registered, and the contours were digitized. The point data released here were extracted from the digitized contour lines and include: latitude, longitude, and magnetic-field value (gamma).