This data release provides digital flight line data for a high-resolution airborne magnetic survey over parts of Montana in the vicinity of the Boulder Batholith. The airborne survey was funded by the Earth Mapping Resources Initiative and was designed to meet complementary needs related to geologic mapping and characterization of mineral resource potential. A total of 45,634 line-km of magnetic data were acquired over an irregular-shaped area of 8,272 km^2. Data were collected from a helicopter flown at a nominal terrain clearance of 100 m above topography along E-W flight lines spaced at 200 m intervals. Tie lines were flown in an N-S direction every 2000 m. Data were collected by Sander Geophysics Limited and Dewberry Engineers, Inc. under contract with the USGS using a helicopter with a magnetometer mounted in a stinger. The survey operated out of the Butte, Montana, airport from July of 2023 to October of 2023. Files that are available in this publication include flight line data for the magnetic survey, a data dictionary, and geoTIFFs of the gridded results.