These polygon features represent the maximum extent of glaciers in Glacier National Park and two glaciers on U.S. Forest Service’s Flathead National Forest land during the peak of the Little Ice Age (mid-nineteenth century). Glacial margins are based on moraine deposits that result from active glaciation, and do not depict perennial snow and ice. The criteria used for determining which moraines constituted a former glacier were a) whether a terminal moraine was present, and b) whether the glacier area was five aces or more. Moraines were digitized based on the best available imagery, including WorldView imagery acquired between 2015 and 2017, border Imagery from the Department of Homeland Security acquired in 2009 and GoogleEarth imagery. High resolution imagery was supplemented with oblique aerial photographs flown in 2009 and 2016, historic photographs from the USGS photograph collection, and field notes from a 1914 USGS survey. Digitization was completed by Chelsea Martin-Mikle (USGS) and local knowledge and interpretation were provided by Dan Fagre and Lisa McKeon (USGS) in February, 2017 – February, 2018. Glacier margins were digitized at 1:2000 scale.