Defining the Last Glacial Maximum (LGM) extent of the Antarctic Ice Sheet on today’s continental shelves remains challenging. Scouring iceberg keels that have largely eradicated potential seafloor evidence, as well as current winnowing and ambiguous dating significantly hamper meaningful reconstructions, particularly on outer shelf regions, where the ice sheet is assumed to have terminated during the LGM. Here we present new geological and geophysical evidence from the outer shelf portion of Abbot Trough in the eastern Amundsen Sea Embayment, reliably showing that this part of the continental shelf was not covered by grounded ice during the last glacial period. This is in contrast to previous reconstructions that suggest a full LGM shelf glaciation, and therefore opens new doors in reconstructing and simulating past ice-sheet conditions, as well as disclosing a new potential site for a glacial refuge, where shelf benthos may have survived the last glacial period.