Jackson Glacier, on the north side of Mount Jackson in Glacier National Park, is one of the park’s most visible and accessible glaciers and now ranks about seventh among its remaining 25 glaciers. First documented in 1850, it was then connected to what is now Blackfoot Glacier in a much larger ice mass covering about 1,875 acres. By 2005, Jackson Glacier alone had shrunk to about 250 acres and had lost nearly a third of its area since 1966. Its retreat reflects the broader loss of ice across the park, making it both a scenic landmark and an important site for U.S. Geological Survey glacier monitoring.