Lake Poinsett is a 3,300-acre natural glacial lake in Hamlin County in eastern South Dakota — the largest natural lake in South Dakota and the centerpiece of the Glacial Lakes region that defines the northeastern South Dakota boating landscape. The lake sits in the Coteau des Prairies — the elevated glacial plateau that separates the James River valley from the Minnesota River valley — surrounded by the productive agricultural land and wetland complexes of eastern South Dakota’s prairie pothole region. Lake Poinsett’s natural basin and prairie shoreline support a walleye, northern pike, yellow perch, and bass fishery managed by the South Dakota Game Fish and Parks. The lake is the flagship of the Glacial Lakes State Park system and draws boaters from across eastern South Dakota and western Minnesota throughout the open water season. Find Boat Services lists verified boat repair, motor service, electronics installation, trailer repair, and winterization providers serving Lake Poinsett within 35 miles across Hamlin, Kingsbury, and Brookings counties. Book fall winterization appointments early — eastern South Dakota’s continental climate brings hard freezes earlier than most Midwest markets and local shops fill winterization schedules quickly in September and October.