We systematically surveyed the Maine coastline from Washington County to York County to provide baseline data concerning Calidris maritima (Purple Sandpiper) population status. Focusing on a particular region each winter, we conducted 66 winter surveys by boat along the entire coast of Maine between 2002 and 2007 plus three days surveying from the mainland between Kittery and Biddeford during the winter of 2005–2006. We tallied 13,318 Purple Sandpipers during these surveys. After accounting for birds present but not detected, we estimate that 14,000 to 17,000 Purple Sandpipers wintered annually in Maine between 2002 and 2007. Based on an assessment of historical records and data collected during this study, flocks of≥250 Purple Sandpipers have been reported from 48 sites along the Maine coast. The area from Isle au Haut to Swans Island along the midcoast supports the highest concentrations of wintering Purple Sandpipers in Maine and the largest wintering concentration of Histrionicus histrionicus (Harlequin Ducks) in eastern North America, highlighting the potential importance of this geographic region.