Airborne electromagnetic (AEM) and magnetic survey data were collected during October 2014 in a 553-square-kilometer area that includes the East Poplar oil field on the Fort Peck Indian Reservation in northeastern Montana, USA. Data surround the city of Poplar and extend south into the Missouri River floodplain. Data were acquired with the SkyTEM301 transient electromagnetic helicopter-borne system together with a Geometrics G-822 magnetometer. The AEM average depth of investigation is about 80 m. The survey was flown at a nominal flight height of 30 m above terrain along north-south oriented flight lines; the majority of lines had a nominal spacing of 200 m with a sub-block area in the central portion of the oil field having 100 m spaced lines. East-west tie lines were flown with a nominal spacing of 8,000 m. The total survey distance is 1,332 line km. This data release includes raw and processed AEM data and spatially-constrained inverted resistivity depth sections along all flight lines. This release also includes unprocessed and processed magnetic data that has been drift corrected and draped to terrain.